Distribution of ABO and Rh blood groups in patients with endometriosis at King Abdulaziz University Hospital: A case control study

Distribution of ABO and Rh blood groups in patients with endometriosis at King Abdulaziz University Hospital: A case control study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Distribution of ABO and Rh blood groups in patients with endometriosis at King Abdulaziz University Hospital: A case control study Maisam H. Alhammadi, Afnan A. Alsaif, Dalal A. Alghamdi, Samera F. AlBasri This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-2628781/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background: There is no sound evidence for the association of blood groups with the risk of endometriosis, and no studies from Saudi Arabia have examined this association. Therefore, the present aim was to determine whether there is an association between the distribution of ABO and Rh blood groups and the incidence of endometriosis in a cohort from Saudi Arabia. Methods: Methods: This case-control study included women diagnosed with endometriosis (n = 44) who presented to King Abdulaziz University Hospital Obstetrics and Gynecology Clinic, Jeddah, Saudi Arabia, between 2010 and 2021. Women from the blood donors database of King Abdulaziz University Hospital were included as a control group (n = 184). The total sample size was 228. Demographic data, diagnosis method, ABO blood type, and Rh blood type were obtained from hospital records. In addition, data were collected from self-reported questionnaires, which included family history, dysmenorrhea, age of menarche, age of childbearing, number of children, history of abortion, parity, number of children, use of oral contraceptives for alleviating dysmenorrhea, iron deficiency, duration of menstrual flow, and volume of bleeding during menses. Odds ratio, Pearson chi-squared test (χ2), and independent t-test were used to analyze the associations between variables. Results: Most of the participants had blood type O (n = 117, 51.3%), which was followed by blood type A (n = 59, 26.0%), and the majority were Rh+ (n = 215, 94.3%). There was no significant difference in the risk of endometriosis according to ABO (P = 0.237) and Rh (P = 0.283) blood types. However, endometriosis was found to have a significant relationship with dysmenorrhea, heavy bleeding during menses, history of abortion, long duration of menstrual flow, lower number of children, late pregnancy, and use of oral contraceptive pills to relieve dysmenorrhea (p ≤ 0.05). Conclusions: The present results indicate that ABO and Rh blood types are not associated with the risk of endometriosis. However, there was a strong, significant association between endometriosis and other factors. Dysmenorrhea abortion infertility ABO blood group Rh blood type endometriosis oral contraceptives heavy menstrual bleeding duration of menses late pregnancy Figures Figure 1 Figure 2 Background The ABO blood group system is based on the presence or absence of certain inherited antigenic glycoproteins on the surface of red blood cells (1). In addition, based on the presence or absence of the D antigen, ABO blood groups are further classified as Rh positive or Rh negative (2). These antigens play an important role in immunologic responses. Endometriosis is an emerging chronic gynecological disease that has a profound impact on the quality of life. It is characterized by the development of tissue resembling the endometrium that is found at sites outside the uterine cavity; it causes pain and could even lead to infertility (3). In addition, it is a chronic inflammatory condition that could lead to scarring, fibrosis, and adhesions in the affected area (4). It affects 10% of reproductive-age women and girls worldwide (190 million) and is associated with infertility in 30% of affected individuals (5). According to previous studies, early age at the first pregnancy, time lag between the first pregnancy and age at menarche, and infertility are risk factors for endometriosis. In addition, a significant association was found between higher levels of education (i.e., college or university degree) and the presence of endometriosis among subjects who underwent diagnostic laparoscopy and hysterectomy (6). With regard to the influence of blood group on the development of endometriosis, a retrospective cohort study conducted at the Yale University Hospital among 230 women with endometriosis suggested that blood group A was associated with a 2.9-fold higher chance of developing endometriosis than other ABO blood groups (7). Further, another study conducted in Paris in a French Caucasian population of 633 patients living in the same geographical area found that Rh-negative women were twice as likely to develop endometriosis (8). In contrast to these findings, a study conducted at the Royan Institute and Arash Women’s Hospital in Iran among 433 women found that there was no significant link between blood groups (ABO/Rh) and the incidence of endometriosis; however, Iranian women with blood type O tended to have a lower chance of developing endometriosis than women with other blood types (9). Further, another Iranian case-control study conducted among 539 participants revealed that there is no significant association between blood type and the occurrence of endometriosis (10). Given these contradictory findings on the association between ABO and Rh blood groups and endometriosis incidence, further studies on more diverse and larger patient groups would be useful for clarifying whether blood type does influence the risk of endometriosis. Further, no studies have investigated the link between ABO and Rh blood types and endometriosis in Jeddah, Saudi Arabia. Therefore, in order to fill in this information gap, this study aimed to determine whether the distribution of ABO and Rh blood groups is associated with the incidence of endometriosis among women who presented to King Abdulaziz University Hospital (KAUH) Obstetrics and Gynecology Clinic, Jeddah, Saudi Arabia. Methods Study design and setting A retrospective case-control study was carried out at KAUH, Jeddah, Saudi Arabia, between June 2021 and December 2021. KAUH is the largest tertiary care hospital in the Western region of Saudi Arabia. It has been accredited by many international accreditation bodies including the Accreditation Canada International, the Joint Commission International, the American Association of Blood Banks, and the College of American Pathologists (11). Study participants The total sample size was 228 women, of whom 44 were in the endometriosis group and 184 were in the control group. The endometriosis group included women with endometriosis who were diagnosed by laparoscopy, laparotomy, or by history taking and physical examination. The control group included female blood donors who were matched with the endometriosis group in terms of their demographic features. Participants with incomplete records were excluded. Data collection Data were collected from patients’ hospital records for the period 2010 to 2020, as well as through a self-reported questionnaire. The research data collected from the hospital records included demographic characteristics, diagnosis method, blood group type (ABO), and Rh blood group (the ABO blood group and Rhesus factor were determined by standard techniques). The rest of the data were obtained via phone calls: family history, dysmenorrhea, age of menarche, age of childbearing, number of children, history of abortion, need for oral contraceptive pills (OCPs) for alleviating dysmenorrhea, iron deficiency, duration of menstrual flow, and volume of bleeding during menses. Research ethics This study was approved by the biomedical ethical committee of KAUH (Ref No. 276-21). All study participants were notified about the research objectives, and their informed consent was obtained prior to commencement of the study. Statistical analysis Microsoft Excel 2016 was used for data entry, and SPSS version 26 was used to analyze the data. To assess the relationship between variables, qualitative data were expressed as numbers and percentages, and the odds ratio, independent samples t -test, and Pearson chi-squared test (χ2) were used to determine the significance of the results. Multivariate logistic regression analysis was also performed to assess the risk factors associated with menstrual irregularities. A p-value of 0.05 was considered to indicate statistical significance. Results The mean age of the participants included in the study was 30 ± 0.23 years, and the majority of the participants were Saudi nationals (n = 183, 80.3%). Most of the participants had blood type O (n = 117, 51.3%), which was followed by A (n = 59, 26.0%), and the majority were Rh+ (n = 215, 94.3%), as shown in Table 1 . With regard to menstrual characteristics, the highest prevalence of endometriosis was recorded for participants who had dysmenorrhea (n = 134, 59%) and those who had never been pregnant (n = 149, 65.6%), as shown in Fig. 1 . Table 1 Distribution of demographic variables, blood groups, and obstetric characteristics in the study cohort (N = 228) Parameters Prevalence n (%) Nationality Saudi 183 (80.3) Non-Saudi 45 (19.8) Blood group O 117 (51.3) A 59 (26.0) AB 12 (5.3) B 40 (17.6) RH factor Positive 215 (94.3) Negative 13 (5.7) Age of childbearing 3 30 (13.2) The endometriosis group was divided according to the diagnosis method: history taking and physical examination (40.91%), laparoscopy (47.7%), and laparotomy (11.4%) (Fig. 2 ). Thus, laparoscopy was the most common diagnostic method, and it was followed by history taking and physical examination. The mean age of the endometriosis group was 35.30 ± 9.37 years, and the mean age of the control group was 29.1 ± 8.14 years (P > 0.001). Thus, women with endometriosis were significantly older than those without endometriosis. The most common ABO blood group was O, with a frequency of 51.1%. There was no significant association between ABO blood group and the presence of endometriosis (P = 0.227). The Rh + blood group was present in 215 women (94.3%). There was no significant correlation between Rh + blood group and risk of endometriosis (P = 0.283, Table 2 ). Table 2 Distribution of combined ABO and Rh blood groups in women with and without endometriosis Variable Endometriosis group (n = 44) n (%) Control group (n = 183) n (%) P value a OR CI P value b Blood group A 12 (27.3) 47 (25.7) 0.227 0.81 0.364–1.79 0.60 B 7 (15.9) 33 (18) 0.97 0.38–2.51 0.95 AB 5 (11.4) 7 (3.8) 0.29 0.08–1.00 0.05 O 20 (45.5) 97 (51.3) Reference Rh factor Rh+ 40 (90.9) 175 (95.1) 0.283 1.94 0.57–6.63 0.29 Rh- 4 (9.1) 9 (4.9) Reference a P value according to Pearson chi-square test b P value according to multiple logistic regression analysis Menstrual characteristics and reproductive history in the case and control groups are shown in Table 3 . A significant relationship was found between endometriosis and dysmenorrhea, heavy bleeding during menses, history of abortion, long duration of menstrual flow (> 7 days), lower number of children, late pregnancy, and use of OCPs to relieve dysmenorrhea (p ≤ 0.05). On the other hand, a non-significant relationship was found between early age of menses (< 11 years), iron deficiency anemia, and family history (p ≥ 0.05). Table 3 Menstrual characteristics, reproductive history, and family history of the study cohort (N = 228) Variable Endometriosis group (n = 44) n (%) Control group (n = 183) n (%) P value a OR a CI P value b Dysmenorrhea Yes 32 (72.7) 102 (55.4) 0.015 0.50 0.24–1.03 0.059 No 12 (27.3) 77 (41.8) Reference Unknown\Not sure 0 (0) 5 (2.7) - Heavy bleeding during menses Yes 22 (50.0) 22 (12.0) 0.000 0.17 0.03–0.83 0.029 No 20 (45.5) 150 (81.5) Reference Unknown\Not sure 2 (4.5) 12 (6.5) 1.25 0.26–5.99 0.78 History of abortion Yes 13 (29.5) 29 (16.3) 0.072 0.465 0.22–0.99 0.047 No 31 (70.5) 154 (83.7) Reference Long duration of menstrual flow (> 7 days) Yes 13 (29.5) 24 (13.0) 0.030 0.358 0.16–0.78 0.009 No 31(70.5) 160 (86.9) Reference Early age of menses (< 11 years) Yes 6 (13.6) 40 (21.7) 0.179 1.76 0.69–4.46 0.234 No 38 (86.4) 143 (78.3) Reference Age of childbearing Before 20 years 7 (15.9) 15 (8.2) 0.000 0.28 0.1–0.77 0.014 20–30 years 16 (36.4) 32 (17.5) 0.24 0.11–0.53 0.000 31–40 years 5 (11.4) 3 (1.6) 0.07 0.02–0.33 0.001 Nulligravida 16 (36.0) 133 (72.3) Reference Number of children Nulliparous 19 (43.2) 138 (75.4) 0.004 Reference 1–3 14 (31.8) 27 (14.7) 0.27 0.12–0.59 0.001 > 4 11 (25.0) 19 (10.3) 0.24 0.1–0.58 0.001 Use of oral contraceptive pills to relieve dysmenorrhea Yes 21 (47.7) 22 (12) 0.00 0.149 0.07–0.31 0.000 No 23 (52.3) 162 (88) Reference Iron deficiency anemia Yes 14 (31.8) 33 (18.0) 0.099 0.48 0.22–1.01 0.13 No 26 (59.1) 129 (70.1) Reference Unknown\Not sure 4 (9.1) 22 (12.0) 1.11 0.35–3.49 0.86 Family history Yes 3 (6.8) 3 (1.6) 0.642 0.85 0.39–1.84 0.68 No 30 (68.2) 138 (75.0) Reference Unknown\Not sure 11 (25.0) 43 (23.4) 0.22 0.04–1.13 0.07 a P value according to Pearson chi-square b P value according to multiple logistic regression analysis Discussion The aim of our research was to determine if the distribution of the ABO and Rh blood groups is associated with endometriosis in women who visit the KAUH Obstetrics and Gynecology Clinic in Jeddah, Saudi Arabia. This is first study to examine this association in a cohort from Saudi Arabia. In a sample of 228 women, we investigated the association of ABO and Rh blood groups with the occurrence of endometriosis and several risk factors and symptoms associated with the disease. The gold standard for the diagnosis of endometriosis is visual inspection via laparoscopy or laparotomy, which was used in more than half of the participants in the current study. However, it is not always feasible in Saudi Arabia to use laparoscopy or laparotomy for routine medical care, and this procedure is not preferred by patients either. Therefore, the rest of the patients were diagnosed based on the clinical presentation, which is applied when the diagnosis can only be established by the patient's medical history, clinical examination, and ultrasound. According to the literature, board-certified gynecologists can identify endometriosis without laparoscopy in 80% of patients (12). In the present study, we found that O was the most common ABO blood group, and the least frequent blood group was AB. Further, the most common Rh blood type was Rh+. These findings are in agreement with studies in Iran conducted by Malekzadeh et al. (9) Pourfathollah et al. (13), and Hosseini et al. (14). With regard to the relationship between blood group and endometriosis risk, neither ABO nor Rh blood types were found to affect the risk of endometriosis, as reported in the study by Daliri et al. (10). However, a research conducted by Borghese et al. in France reported that Rh- women are twice as likely to have endometriosis, while Demir et al. (15) reported that the risk of endometriosis in Rh + women was significantly higher than that of the control group. The differences between these studies might attributable to genetic variations among the study participants, as ethnicity, time, and geographic region are some of the known factors that affect the distribution of the Rh and ABO blood groups(9). The findings of the current study demonstrated that the majority of the participants reported having dysmenorrhea, and a significant association was found between dysmenorrhea and the occurrence of endometriosis. Accordingly, it is known that endometriosis is the most common cause of secondary dysmenorrhea. In addition, we found that the incidence of heavy bleeding was higher among women with endometriosis. However, in contrast to our findings, several other studies have demonstrated that there is no association between menstruation-related factors and endometriosis (16). The difference in the results of… Several studies have demonstrated that patients with a family history of endometriosis have a seven-fold higher risk of endometriosis (17). In contrast, our results show that there was no significant association with family history. This is most likely the result of a lack of diagnosis or ignorance of the condition previously in the family. Our study also revealed a substantial link between endometriosis and the use of OCPs, which are used as the initial treatment for dysmenorrhea in young women (12). In addition, late pregnancy issues and nulliparity were more prevalent in endometriosis-affected women, as evidenced by previous findings too (17). Thus, endometriosis may be associated with the use of OCPs, late pregnancy and nulliparity. Limitations Some limitations in our study should be considered. The study was limited to participants from one center and had a limited sample size, which may not represent the general population of women in Jeddah. Further, as part of the data were self-reported, some of the results may be skewed due to recall bias. Finally, as this is a retrospective case-control study, the causative relationship between factors could not be established, even though endometriosis showed a significant correlation with a few menstruation-related factors. Conclusion This study found no significant association between the main blood groups (ABO and Rh) and the risk of endometriosis. However, the evidence is not sufficient to confirm/reject the hypothesis that the ABO system could be a genetic risk factor for the development of endometriosis, and further studies on larger samples and with more genetic factors are required. Declarations Ethics approval and consent to participate Before the participants completed the questionnaire, they were informed about the objectives of the study and assured of the confidentiality of their information, and their written informed consent was obtained. The Ethics Committee of King Abdulaziz University Hospital provided ethical approval for the study (Ref No. 276-21). We confirm that all methods were carried out in accordance with relevant guidelines and regulations. Consent for publication Not applicable Availability of data and materials The corresponding author can provide access to the datasets generated and analyzed during the current investigation based on request at any time. Competing interests The authors declare that they have no competing interests. Authors’ contributions Maisam Alhammadi, Afnan Alsaif, and Dalal Alghamdi participated in writing the original draft of this manuscript and data collection. All the authors listed have sufficiently contributed to the development, editorial changes, and final approval of the final manuscript. Dr Samera AlBasri edited the main manuscript text. All authors read and approved the final manuscript. Ethics declaration The research study has been approved by KAU research committee (Ref No. 276-21) and all the methods done following the relevant guidelines. Funding No funding was obtained for this study. Acknowledgments We especially thank Dr. Maha Badawi for her assistance in retrieving control group data which we used in our project, and Alwa Almontashri for her contribution in data collection. References McPherson RA, Pincus MR. Henry's clinical diagnosis and management by laboratory methods E-book. Elsevier Health Sciences; 2021 Jun 9. Valikhani M, Kavand S, Toosi S, Kavand G, Ghiasi M. ABO blood groups, rhesus factor and pemphigus. Indian J Dermatol. 2007 Oct 1;52(4):176. World Health Organization (WHO). International Classification of Diseases, 11th Revision (ICD-11) Geneva: WHO 2018. Endometriosis. 2021, March 31. https://www.who.int/news-room/fact-sheets/detail/endometriosis. Accessed X March, XXXX. Zondervan KT, Becker CM, Missmer SA. Endometriosis. N Engl J Med. 2020 Mar 26;382(13):1244–1256. doi: 10.1056/NEJMra1810764. PMID: 32212520. Hemmings R, Rivard M, Olive DL, Poliquin-Fleury J, Gagné D, Hugo P, Gosselin D. Evaluation of risk factors associated with endometriosis. Fertility and sterility. 2004 Jun 1;81(6):1513-21. Matalliotakis I, Cakmak H, Goumenou A, Sifakis S, Ziogos E, Arici A. ABO and Rh blood groups distribution in patients with endometriosis. Arch Gynecol Obstet [Internet]. 2009 Dec [cited 2021 Mar 11];280(6):917–9. Available from: https://pubmed.ncbi.nlm.nih.gov/19301022/ Borghese B, Chartier M, Souza C, Santulli P, Lafay-Pillet MC, De Ziegler D, et al. ABO and Rhesus Blood Groups and Risk of Endometriosis in a French Caucasian Population of 633 Patients Living in the Same Geographic Area. Biomed Res Int [Internet]. 2014 [cited 2021 Mar 11];2014. Available from: https://pubmed.ncbi.nlm.nih.gov/25243164/ Malekzadeh F, Moini A, Amirchaghmaghi E, Daliri L, Akhoond MR, Talebi M, et al. The association between ABO and Rh blood groups and risk of endometriosis in iranian women. Int J Fertil Steril [Internet]. 2018 Oct 1 [cited 2021 Mar 11];12(3):213–7. Available from: https://pubmed.ncbi.nlm.nih.gov/29935066/ Daliri K, Tabei SM, Amini A, Derakhshankhah H. Are ABO and Rh blood groups new genetic risk factors for endometriosis? Arch Gynecol Obstet [Internet]. 2013 Apr 18 [cited 2021 Apr 3];288(5):961–3. Available from: https://link.springer.com/article/10.1007/s00404-013-2844-6 KAU Hospital - About Hospital.” KAU Hospital - About Hospital, hospital.kau.edu.sa/Content-599-EN-38308. Accessed 3 Feb. 2023. Harada T. Dysmenorrhea and endometriosis in young women. Yonago Acta Med. 2013 Dec;56(4):81 − 4. Epub 2013 Nov 28. PMID: 24574576; PMCID: PMC3935015. Pourfathollah AA, Oody A, Honarkaran N. Geographical distribution of ABO and Rh (D) blood groups among Iranian blood donors in the year 1361 (1982) as compared with that of the year 1380 (2001). Scientific Journal of Iran Blood Transfus Organ. 2004 Nov 10;1(1):11 − 7. Hosseini MM, Baniaghil SS, Balkhi MR, Seyedein MS. Frequency distribution of blood groups ABO and Rh in the population of blood donors in Golestan province during 2006–2010. Scientific Journal of Iran Blood Transfus Organ. 2012 Oct 10;9(3):358 − 62. Demir B, Dilbaz B, Zahran M. ABO and Rh blood groups distribution in patients with endometriosis. Archives of gynecology and obstetrics. 2010 Feb; 281:373-4. Hemmings R, Rivard M, Olive DL, Poliquin-Fleury J, Gagné D, Hugo P, Gosselin D. Evaluation of risk factors associated with endometriosis. Fertility and sterility. 2004 Jun 1;81(6):1513-21. Moen MH, Magnus P. The familial risk of endometriosis. Acta obstetricia et gynecologica Scandinavica. 1993 Jan 1;72(7):560-4. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-2628781","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":182418228,"identity":"b878b494-6672-425b-b59a-d4a234a009fe","order_by":0,"name":"Maisam H. 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In addition, based on the presence or absence of the D antigen, ABO blood groups are further classified as Rh positive or Rh negative (2). These antigens play an important role in immunologic responses.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eEndometriosis is an emerging chronic gynecological disease that has a profound impact on the quality of life. It is characterized by the development of tissue resembling the endometrium that is found at sites outside the uterine cavity; it causes pain and could even lead to infertility \u0026nbsp; \u0026nbsp; \u0026nbsp;(3). In addition, it is a chronic inflammatory condition that could lead to scarring, fibrosis, and adhesions in the affected area \u0026nbsp;(4). It affects 10% of reproductive-age women and girls worldwide (190 million) and is associated with infertility in 30% of affected individuals (5). According to previous studies, early age at the first pregnancy, time lag between the first pregnancy and age at menarche, and infertility are risk factors for endometriosis. In addition, a significant association was found between higher levels of education (i.e., college or university degree) and the presence of endometriosis among subjects who underwent diagnostic laparoscopy and hysterectomy \u0026nbsp;(6). With regard to the influence of blood group on the development of endometriosis, a retrospective cohort study conducted at the Yale University Hospital among 230 women with endometriosis suggested that blood group A was associated with a 2.9-fold higher chance of developing endometriosis than other ABO blood groups (7). Further, another study conducted in Paris in a French Caucasian population of 633 patients living in the same geographical area found that Rh-negative women were twice as likely to develop endometriosis (8). In contrast to these findings, a study conducted at the Royan Institute and Arash Women\u0026rsquo;s Hospital in Iran among 433 women found that there was no significant link between blood groups (ABO/Rh) and the incidence of endometriosis; however, Iranian women with blood type O tended to have a lower chance of developing endometriosis than women with other blood types (9). Further, another Iranian case-control study conducted among 539 participants revealed that there is no significant association between blood type and the occurrence of endometriosis (10). Given these contradictory findings on the association between ABO and Rh blood groups and endometriosis incidence, further studies on more diverse and larger patient groups would be useful for clarifying whether blood type does influence the risk of endometriosis. Further, no studies have investigated the link between ABO and Rh blood types and endometriosis in Jeddah, Saudi Arabia. Therefore, in order to fill in this information gap, this study aimed to determine whether the distribution of ABO and Rh blood groups is associated with the incidence of endometriosis among women who presented to King Abdulaziz University Hospital (KAUH) Obstetrics and Gynecology Clinic, Jeddah, Saudi Arabia.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cstrong\u003eStudy design and setting\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA retrospective case-control study was carried out at KAUH, Jeddah, Saudi Arabia, between June 2021 and December 2021. KAUH is the largest tertiary care hospital in the Western region of Saudi Arabia. It\u0026nbsp;has\u0026nbsp;been accredited by many international accreditation bodies including the Accreditation Canada International, the Joint Commission\u0026nbsp;International, the\u0026nbsp;American Association of Blood Banks, and the College of American\u0026nbsp;Pathologists\u0026nbsp;(11).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;Study participants\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe total sample size was\u0026nbsp;228\u0026nbsp;women, of whom 44 were in the endometriosis group and 184\u0026nbsp;were in the control\u0026nbsp;group. The endometriosis group included women with\u0026nbsp;endometriosis who were\u0026nbsp;diagnosed by laparoscopy, laparotomy, or by history taking and physical examination. The control\u0026nbsp;group\u0026nbsp;included female blood donors who were\u0026nbsp;matched with the endometriosis group in terms of their demographic features. Participants with incomplete records were excluded.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;Data collection\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData were collected from patients\u0026rsquo; hospital records for the period 2010 to 2020, as well as through a self-reported questionnaire. The research data collected from the hospital records included demographic characteristics, diagnosis method, blood group type (ABO), and Rh blood group (the ABO blood group and Rhesus factor were determined by standard techniques). The rest of the data were obtained via phone calls: family history, dysmenorrhea, age of menarche, age of childbearing, number of children, history of abortion, need for oral contraceptive pills (OCPs) for alleviating dysmenorrhea, iron deficiency, duration of menstrual flow, and volume of bleeding during menses.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResearch ethics\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;This study was approved by the biomedical ethical committee of KAUH (Ref No. 276-21). All study participants were notified about the research objectives, and their informed consent was obtained prior to commencement of the study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatistical analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMicrosoft Excel 2016 was used for data entry, and SPSS version 26 was used to analyze the data. To assess the relationship between variables, qualitative data were expressed as numbers and percentages, and the odds ratio, independent samples \u003cem\u003et\u003c/em\u003e-test, and Pearson chi-squared test (\u0026chi;2) were used to determine the significance of the results. Multivariate logistic regression analysis was also performed to assess the risk factors associated with menstrual irregularities. A p-value of 0.05 was considered to indicate statistical significance.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eThe mean age of the participants included in the study was 30\u0026thinsp;\u0026plusmn;\u0026thinsp;0.23 years, and the majority of the participants were Saudi nationals (n\u0026thinsp;=\u0026thinsp;183, 80.3%). Most of the participants had blood type O (n\u0026thinsp;=\u0026thinsp;117, 51.3%), which was followed by A (n\u0026thinsp;=\u0026thinsp;59, 26.0%), and the majority were Rh+ (n\u0026thinsp;=\u0026thinsp;215, 94.3%), as shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. With regard to menstrual characteristics, the highest prevalence of endometriosis was recorded for participants who had dysmenorrhea (n\u0026thinsp;=\u0026thinsp;134, 59%) and those who had never been pregnant (n\u0026thinsp;=\u0026thinsp;149, 65.6%), as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDistribution of demographic variables, blood groups, and obstetric characteristics in the study cohort (N\u0026thinsp;=\u0026thinsp;228)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePrevalence\u003c/p\u003e \u003cp\u003en (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNationality\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSaudi\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e183 (80.3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNon-Saudi\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e45 (19.8)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eBlood group\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e117 (51.3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e59 (26.0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12 (5.3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e40 (17.6)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eRH factor\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePositive\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e215 (94.3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNegative\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e13 (5.7)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAge of childbearing\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;20 years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e23 (10.1)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e20\u0026ndash;30 years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e48 (21.1)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e31\u0026ndash;40 years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8 (3.5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNulligravida (never been pregnant)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e149 (65.4)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eNumber of children\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNulliparous (never had children)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e157 (68.9)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u0026ndash;3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e41 (18.0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30 (13.2)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe endometriosis group was divided according to the diagnosis method: history taking and physical examination (40.91%), laparoscopy (47.7%), and laparotomy (11.4%) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Thus, laparoscopy was the most common diagnostic method, and it was followed by history taking and physical examination.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe mean age of the endometriosis group was 35.30\u0026thinsp;\u0026plusmn;\u0026thinsp;9.37 years, and the mean age of the control group was 29.1\u0026thinsp;\u0026plusmn;\u0026thinsp;8.14 years (P\u0026thinsp;\u0026gt;\u0026thinsp;0.001). Thus, women with endometriosis were significantly older than those without endometriosis. The most common ABO blood group was O, with a frequency of 51.1%. There was no significant association between ABO blood group and the presence of endometriosis (P\u0026thinsp;=\u0026thinsp;0.227). The Rh\u0026thinsp;+\u0026thinsp;blood group was present in 215 women (94.3%). There was no significant correlation between Rh\u0026thinsp;+\u0026thinsp;blood group and risk of endometriosis (P\u0026thinsp;=\u0026thinsp;0.283, Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDistribution of combined ABO and Rh blood groups in women with and without endometriosis\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEndometriosis group\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;44)\u003c/p\u003e \u003cp\u003en (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eControl group\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;183)\u003c/p\u003e \u003cp\u003en (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP value\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eOR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eCI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eP value\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"7\" nameend=\"c7\" namest=\"c1\"\u003e \u003cp\u003eBlood group\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eA\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12 (27.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e47 (25.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e0.227\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.364\u0026ndash;1.79\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.60\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eB\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7 (15.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e33 (18)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.38\u0026ndash;2.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.95\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAB\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5 (11.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7 (3.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.08\u0026ndash;1.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e0.05\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eO\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20 (45.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e97 (51.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eRh factor\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eRh+\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e40 (90.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e175 (95.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.283\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.57\u0026ndash;6.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.29\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eRh-\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4 (9.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9 (4.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003e\u003csup\u003e\u003cb\u003ea\u003c/b\u003e\u003c/sup\u003e\u003cb\u003eP value according to Pearson chi-square test\u003c/b\u003e\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003e\u003csup\u003e\u003cb\u003eb\u003c/b\u003e\u003c/sup\u003e\u003cb\u003eP value according to multiple logistic regression analysis\u003c/b\u003e\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eMenstrual characteristics and reproductive history in the case and control groups are shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. A significant relationship was found between endometriosis and dysmenorrhea, heavy bleeding during menses, history of abortion, long duration of menstrual flow (\u0026gt;\u0026thinsp;7 days), lower number of children, late pregnancy, and use of OCPs to relieve dysmenorrhea (p\u0026thinsp;\u0026le;\u0026thinsp;0.05). On the other hand, a non-significant relationship was found between early age of menses (\u0026lt;\u0026thinsp;11 years), iron deficiency anemia, and family history (p\u0026thinsp;\u0026ge;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMenstrual characteristics, reproductive history, and family history of the study cohort (N\u0026thinsp;=\u0026thinsp;228)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEndometriosis group\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;44)\u003c/p\u003e \u003cp\u003en (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eControl group\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;183)\u003c/p\u003e \u003cp\u003en (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP value\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eOR\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eCI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eP value\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDysmenorrhea\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e32 (72.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e102 (55.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e\u003cb\u003e0.015\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.24\u0026ndash;1.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e0.059\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12 (27.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e77 (41.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUnknown\\Not sure\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0 (0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5 (2.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eHeavy bleeding during menses\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e22 (50.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22 (12.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e\u003cb\u003e0.000\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.03\u0026ndash;0.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e0.029\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20 (45.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e150 (81.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUnknown\\Not sure\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2 (4.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12 (6.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.26\u0026ndash;5.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.78\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eHistory of abortion\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e13 (29.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e29 (16.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.072\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.465\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.22\u0026ndash;0.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003e0.047\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e31 (70.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e154 (83.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"7\" nameend=\"c7\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLong duration of menstrual flow (\u0026gt;\u0026thinsp;7 days)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e13 (29.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e24 (13.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003e0.030\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.358\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.16\u0026ndash;0.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003e0.009\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e31(70.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e160 (86.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"7\" nameend=\"c7\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eEarly age of menses (\u0026lt;\u0026thinsp;11 years)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6 (13.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e40 (21.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.179\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.69\u0026ndash;4.46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.234\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e38 (86.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e143 (78.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"7\" nameend=\"c7\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAge of childbearing\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBefore 20 years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7 (15.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15 (8.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.000\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.1\u0026ndash;0.77\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e0.014\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e20\u0026ndash;30 years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16 (36.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e32 (17.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.11\u0026ndash;0.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e0.000\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e31\u0026ndash;40 years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5 (11.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3 (1.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.02\u0026ndash;0.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNulligravida\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16 (36.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e133 (72.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"7\" nameend=\"c7\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eNumber of children\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNulliparous\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e19 (43.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e138 (75.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.004\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u0026ndash;3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e14 (31.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e27 (14.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.12\u0026ndash;0.59\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11 (25.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e19 (10.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.1\u0026ndash;0.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"7\" nameend=\"c7\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eUse of oral contraceptive pills to relieve dysmenorrhea\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e21 (47.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22 (12)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.00\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.149\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.07\u0026ndash;0.31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003e0.000\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e23 (52.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e162 (88)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"7\" nameend=\"c7\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eIron deficiency anemia\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e14 (31.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e33 (18.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.099\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.22\u0026ndash;1.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.13\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e26 (59.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e129 (70.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUnknown\\Not sure\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4 (9.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22 (12.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.35\u0026ndash;3.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.86\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eFamily history\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3 (6.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3 (1.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.642\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.39\u0026ndash;1.84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.68\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30 (68.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e138 (75.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUnknown\\Not sure\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11 (25.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e43 (23.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.04\u0026ndash;1.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.07\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003e\u003csup\u003e\u003cb\u003ea\u003c/b\u003e\u003c/sup\u003e\u003cb\u003eP value according to Pearson chi-square\u003c/b\u003e\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003e\u003csup\u003e\u003cb\u003eb\u003c/b\u003e\u003c/sup\u003e\u003cb\u003eP value according to multiple logistic regression analysis\u003c/b\u003e\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe aim of our research was to determine if the distribution of the ABO and Rh blood groups is associated with endometriosis in women who visit the KAUH Obstetrics and Gynecology Clinic in Jeddah, Saudi Arabia. This is first study to examine this association in a cohort from Saudi Arabia. In a sample of 228 women, we investigated the association of ABO and Rh blood groups with the occurrence of endometriosis and several risk factors and symptoms associated with the disease.\u003c/p\u003e \u003cp\u003eThe gold standard for the diagnosis of endometriosis is visual inspection via laparoscopy or laparotomy, which was used in more than half of the participants in the current study. However, it is not always feasible in Saudi Arabia to use laparoscopy or laparotomy for routine medical care, and this procedure is not preferred by patients either. Therefore, the rest of the patients were diagnosed based on the clinical presentation, which is applied when the diagnosis can only be established by the patient's medical history, clinical examination, and ultrasound. According to the literature, board-certified gynecologists can identify endometriosis without laparoscopy in 80% of patients (12).\u003c/p\u003e \u003cp\u003eIn the present study, we found that O was the most common ABO blood group, and the least frequent blood group was AB. Further, the most common Rh blood type was Rh+. These findings are in agreement with studies in Iran conducted by Malekzadeh et al. (9) Pourfathollah et al. (13), and Hosseini et al. (14). With regard to the relationship between blood group and endometriosis risk, neither ABO nor Rh blood types were found to affect the risk of endometriosis, as reported in the study by Daliri et al. (10). However, a research conducted by Borghese et al. in France reported that Rh- women are twice as likely to have endometriosis, while Demir et al. (15) reported that the risk of endometriosis in Rh\u0026thinsp;+\u0026thinsp;women was significantly higher than that of the control group. The differences between these studies might attributable to genetic variations among the study participants, as ethnicity, time, and geographic region are some of the known factors that affect the distribution of the Rh and ABO blood groups(9).\u003c/p\u003e \u003cp\u003eThe findings of the current study demonstrated that the majority of the participants reported having dysmenorrhea, and a significant association was found between dysmenorrhea and the occurrence of endometriosis. Accordingly, it is known that endometriosis is the most common cause of secondary dysmenorrhea. In addition, we found that the incidence of heavy bleeding was higher among women with endometriosis. However, in contrast to our findings, several other studies have demonstrated that there is no association between menstruation-related factors and endometriosis (16). The difference in the results of\u0026hellip;\u003c/p\u003e \u003cp\u003eSeveral studies have demonstrated that patients with a family history of endometriosis have a seven-fold higher risk of endometriosis (17). In contrast, our results show that there was no significant association with family history. This is most likely the result of a lack of diagnosis or ignorance of the condition previously in the family. Our study also revealed a substantial link between endometriosis and the use of OCPs, which are used as the initial treatment for dysmenorrhea in young women (12). In addition, late pregnancy issues and nulliparity were more prevalent in endometriosis-affected women, as evidenced by previous findings too (17). Thus, endometriosis may be associated with the use of OCPs, late pregnancy and nulliparity.\u003c/p\u003e\n\u003ch3\u003eLimitations\u003c/h3\u003e\n\u003cp\u003eSome limitations in our study should be considered. The study was limited to participants from one center and had a limited sample size, which may not represent the general population of women in Jeddah. Further, as part of the data were self-reported, some of the results may be skewed due to recall bias. Finally, as this is a retrospective case-control study, the causative relationship between factors could not be established, even though endometriosis showed a significant correlation with a few menstruation-related factors.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis study found no significant association between the main blood groups (ABO and Rh) and the risk of endometriosis. However, the evidence is not sufficient to confirm/reject the hypothesis that the ABO system could be a genetic risk factor for the development of endometriosis, and further studies on larger samples and with more genetic factors are required.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eBefore the participants completed the questionnaire, they were informed about the objectives of the study and assured of the confidentiality of their information, and their written informed consent was obtained. The Ethics Committee of King Abdulaziz University Hospital provided ethical approval for the study (Ref No. 276-21). We confirm that all methods were carried out in accordance with relevant guidelines and regulations.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication \u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe corresponding\u0026nbsp;author can provide access to the datasets generated and analyzed during the current investigation based on request at any time.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests \u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;Authors\u0026rsquo; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMaisam Alhammadi, Afnan Alsaif, and Dalal Alghamdi participated in writing the original\u0026nbsp;draft\u0026nbsp;of this manuscript and data collection. All the authors listed have sufficiently contributed to the development, editorial changes, and final approval of the final manuscript. Dr Samera AlBasri edited the main manuscript text. All authors read and approved the final manuscript.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics declaration\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe research study has been approved by KAU research committee (Ref No. 276-21) and all the methods done following the relevant guidelines.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo funding was obtained for this study.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe especially thank Dr. Maha Badawi for her assistance in retrieving control group data which we used in our project, and Alwa Almontashri for her contribution in data collection.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eMcPherson RA, Pincus MR. Henry's clinical diagnosis and management by laboratory methods E-book. Elsevier Health Sciences; 2021 Jun 9.\u003c/li\u003e\n\u003cli\u003eValikhani M, Kavand S, Toosi S, Kavand G, Ghiasi M. ABO blood groups, rhesus factor and pemphigus. Indian J Dermatol. 2007 Oct 1;52(4):176.\u003c/li\u003e\n\u003cli\u003eWorld Health Organization (WHO). International Classification of Diseases, 11th Revision (ICD-11) Geneva: WHO 2018.\u003c/li\u003e\n\u003cli\u003eEndometriosis. 2021, March 31. https://www.who.int/news-room/fact-sheets/detail/endometriosis. Accessed X March, XXXX.\u003c/li\u003e\n\u003cli\u003eZondervan KT, Becker CM, Missmer SA. Endometriosis. N Engl J Med. 2020 Mar 26;382(13):1244\u0026ndash;1256. doi: 10.1056/NEJMra1810764. PMID: 32212520.\u003c/li\u003e\n\u003cli\u003eHemmings R, Rivard M, Olive DL, Poliquin-Fleury J, Gagn\u0026eacute; D, Hugo P, Gosselin D. Evaluation of risk factors associated with endometriosis. Fertility and sterility. 2004 Jun 1;81(6):1513-21.\u003c/li\u003e\n\u003cli\u003eMatalliotakis I, Cakmak H, Goumenou A, Sifakis S, Ziogos E, Arici A. ABO and Rh blood groups distribution in patients with endometriosis. Arch Gynecol Obstet [Internet]. 2009 Dec [cited 2021 Mar 11];280(6):917\u0026ndash;9. Available from: https://pubmed.ncbi.nlm.nih.gov/19301022/\u003c/li\u003e\n\u003cli\u003eBorghese B, Chartier M, Souza C, Santulli P, Lafay-Pillet MC, De Ziegler D, et al. ABO and Rhesus Blood Groups and Risk of Endometriosis in a French Caucasian Population of 633 Patients Living in the Same Geographic Area. Biomed Res Int [Internet]. 2014 [cited 2021 Mar 11];2014. Available from: https://pubmed.ncbi.nlm.nih.gov/25243164/\u003c/li\u003e\n\u003cli\u003eMalekzadeh F, Moini A, Amirchaghmaghi E, Daliri L, Akhoond MR, Talebi M, et al. The association between ABO and Rh blood groups and risk of endometriosis in iranian women. Int J Fertil Steril [Internet]. 2018 Oct 1 [cited 2021 Mar 11];12(3):213\u0026ndash;7. Available from: https://pubmed.ncbi.nlm.nih.gov/29935066/\u003c/li\u003e\n\u003cli\u003eDaliri K, Tabei SM, Amini A, Derakhshankhah H. Are ABO and Rh blood groups new genetic risk factors for endometriosis? Arch Gynecol Obstet [Internet]. 2013 Apr 18 [cited 2021 Apr 3];288(5):961\u0026ndash;3. Available from: https://link.springer.com/article/10.1007/s00404-013-2844-6\u003c/li\u003e\n\u003cli\u003eKAU Hospital - About Hospital.\u0026rdquo; KAU Hospital - About Hospital, hospital.kau.edu.sa/Content-599-EN-38308. Accessed 3 Feb. 2023.\u003c/li\u003e\n\u003cli\u003eHarada T. Dysmenorrhea and endometriosis in young women. Yonago Acta Med. 2013 Dec;56(4):81\u0026thinsp;\u0026minus;\u0026thinsp;4. Epub 2013 Nov 28. PMID: 24574576; PMCID: PMC3935015.\u003c/li\u003e\n\u003cli\u003ePourfathollah AA, Oody A, Honarkaran N. Geographical distribution of ABO and Rh (D) blood groups among Iranian blood donors in the year 1361 (1982) as compared with that of the year 1380 (2001). Scientific Journal of Iran Blood Transfus Organ. 2004 Nov 10;1(1):11\u0026thinsp;\u0026minus;\u0026thinsp;7.\u003c/li\u003e\n\u003cli\u003eHosseini MM, Baniaghil SS, Balkhi MR, Seyedein MS. Frequency distribution of blood groups ABO and Rh in the population of blood donors in Golestan province during 2006\u0026ndash;2010. Scientific Journal of Iran Blood Transfus Organ. 2012 Oct 10;9(3):358\u0026thinsp;\u0026minus;\u0026thinsp;62.\u003c/li\u003e\n\u003cli\u003eDemir B, Dilbaz B, Zahran M. ABO and Rh blood groups distribution in patients with endometriosis. Archives of gynecology and obstetrics. 2010 Feb; 281:373-4.\u003c/li\u003e\n\u003cli\u003eHemmings R, Rivard M, Olive DL, Poliquin-Fleury J, Gagn\u0026eacute; D, Hugo P, Gosselin D. Evaluation of risk factors associated with endometriosis. Fertility and sterility. 2004 Jun 1;81(6):1513-21.\u003c/li\u003e\n\u003cli\u003eMoen MH, Magnus P. The familial risk of endometriosis. Acta obstetricia et gynecologica Scandinavica. 1993 Jan 1;72(7):560-4.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Dysmenorrhea, abortion, infertility, ABO blood group, Rh blood type, endometriosis, oral contraceptives, heavy menstrual bleeding, duration of menses, late pregnancy","lastPublishedDoi":"10.21203/rs.3.rs-2628781/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-2628781/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground:\u003c/strong\u003e There is no sound evidence for the association of blood groups with the risk of endometriosis, and no studies from Saudi Arabia have examined this association. Therefore, the present aim was to determine whether there is an association between the distribution of ABO and Rh blood groups and the incidence of endometriosis in a cohort from Saudi Arabia.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods:\u003c/strong\u003e Methods: This case-control study included women diagnosed with endometriosis (n = 44) who presented to King Abdulaziz University Hospital Obstetrics and Gynecology Clinic, Jeddah, Saudi Arabia, between 2010 and 2021. Women from the blood donors database of King Abdulaziz University Hospital were included as a control group (n = 184). The total sample size was 228. Demographic data, diagnosis method, ABO blood type, and Rh blood type were obtained from hospital records. In addition, data were collected from self-reported questionnaires, which included family history, dysmenorrhea, age of menarche, age of childbearing, number of children, history of abortion, parity, number of children, use of oral contraceptives for alleviating dysmenorrhea, iron deficiency, duration of menstrual flow, and volume of bleeding during menses. Odds ratio, Pearson chi-squared test (χ2), and independent t-test were used to analyze the associations between variables.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e Most of the participants had blood type O (n = 117, 51.3%), which was followed by blood type A (n = 59, 26.0%), and the majority were Rh+ (n = 215, 94.3%). There was no significant difference in the risk of endometriosis according to ABO (P = 0.237) and Rh (P = 0.283) blood types. However, endometriosis was found to have a significant relationship with dysmenorrhea, heavy bleeding during menses, history of abortion, long duration of menstrual flow, lower number of children, late pregnancy, and use of oral contraceptive pills to relieve dysmenorrhea (p ≤ 0.05).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions:\u003c/strong\u003e The present results indicate that ABO and Rh blood types are not associated with the risk of endometriosis. However, there was a strong, significant association between endometriosis and other factors.\u003c/p\u003e","manuscriptTitle":"Distribution of ABO and Rh blood groups in patients with endometriosis at King Abdulaziz University Hospital: A case control study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-03-16 14:09:09","doi":"10.21203/rs.3.rs-2628781/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"738bd2c7-e248-485f-aa8d-f5baa7e58eb1","owner":[],"postedDate":"March 16th, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2023-06-22T11:59:23+00:00","versionOfRecord":[],"versionCreatedAt":"2023-03-16 14:09:09","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-2628781","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-2628781","identity":"rs-2628781","version":["v1"]},"buildId":"B-jG_2CBjPDmsCi4Wdhf-","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}