{"paper_id":"f03bdf66-6a47-4b7c-8d37-9d2d1ece9d3a","body_text":"Endometriosis is a prolonged, benign and progressive\ninflammatory gynecological disease. It is defined as\nthe existence of endometrial tissue outside the uterine\ncavity ( 1 ,  2 ). The pelvic cavity was the most frequent\nsite of endometriosis lesions may involve the uterosacral\nligament, ovaries, and Douglas’ pouch ( 3 ). Approximately\nten percent of women of the reproductive age (176\nmillion) are affected by endometriosis worldwide ( 4 - 7 ).\nIt is associated with a number of symptoms that can be\ndisturbing for patients and affect their quality of life ( 8 ,  9 ).\nThe prevalence of endometriosis in symptomatic women\nestimates up to 75% ( 10 - 12 ). The laparoscopy findings\nof a study conducted on the 441 infertile Iranian women\nindicated that the prevalence of endometriosis was about\n18.6% ( 10 ). Endometriosis is often labeled “the missed\ndisease” ( 13 ). Endometriosis may be existent for a long\ntime before it is detected ( 14 ). The ordinary age of the\ndiagnosis is about 25-29 years old, while the overall delay\nin diagnosis, especially in European countries, is about\n5-10 years ( 15 ,  16 ).\nIt is noteworthy that the etiology and pathogenesis of\nendometriosis are poorly understood ( 17 ). It develops\ndue to factors such as hormonal imbalances ( 11 )\ngenetic alteration , and changes in the immune system\n( 18 - 20 ).\nLack of established theory of endometriosis\nexpressions of the retrograde menstruation is generally\naccepted to define the spread of endometrial soft tissue\nto the peritoneal cavity during the open fallopian\ntubes during menstruation ( 17 ,  18 ). In this way,\nstudies on the uterine pressure during menstruation\nrevealed that the contraction of the fallopian tubes and\nmyometrium considerably increases during ovulation\nand menstruation ( 21 ). It supposes that the volume\nand level of retrograde menstruation play an essential\nrole in the emergence and progress development\nand severity of the endometriosis ( 22 ). There is a\nhypothesis that sexual activity during menstruation\ncan surge retrograde menstruation, planting tissue of\nendometrium elsewhere, and thus elevating risk of\nendometriosis ( 23 ). According to the results of studies\nthat have considered the relationship between sexual\nactivity during menstruation and endometriosis;\nendometriosis in women who had sexual intercourse\nduring menstruation, was higher in comparison with\nwhom abstinence from sexual intercourse in the same\ntime ( 23 - 25 ). The results of another study showed\nthat sexual activity during menstruation was lower\nin women with endometriosis compared to women\nwithout endometriosis ( 26 ). Although, limited studies\nhave been performed to assess the effect of sexual\nactivity during menstruation on the endometriosis,\nthere are important issues that must not be neglected\nsuch as quality of life of women of reproductive age\n( 13 ,  16 ,  27 ,  28 ), and fertility of affected women. The\npresent systematic review and meta-analysis aimed\nto answer to the question of whether sexual activity\nduring menstruation can be related to the occurrence of\nendometriosis.\n\nThis review was carried out according to the Preferred Reporting Items for Systematic\nReviews and MetaAnalyses (PRISMA) statement. It was limited to the published research\narticles that compared sexual activity during menstruation in women with and without\nendometriosis. The Participant, Intervention, Control group, Outcome (PICO) model was used\nas a search tool in which; i. Participants: women with confirmed endometriosis diagnosis,\nii. Interventions: none, iii. Control group: women without endometriosis, iv. Outcome:\nendometriosis affected women. Two members of our team checked all published studies,\nnational and international databases, including Medline (via PubMed), Web of Science,\nScopus, and ProQuest as well as Persian databases consisting of SID, Magiran, Iranmedex.\nAlso, they restricted their search to English and Persian languages until September\n21 st , 2021. Finally, the reference list of retrieved studies was manually\nsearched to find further relevant studies. We excluded the Grey literature, that did not\npass the peerreviewed process and also, not available at the time of this analysis. These\nincluded abstracts, conferences, proceedings, presentations, unpublished data, regulatory\ndata, government publications, dissertations/theses, reports, patents, as well as policies\nand procedures. To search databases, keywords of sexual activity, sexual intercourse,\nsexual behavior, menstruation, menstrual bleeding, menstrual cycle, endometriosis and\nsystematic reviews with their equivalent words in MeSH as well as their combination with\neach other were searched using Boolean operators (AND as well as OR). The PRISMA 2020\nflowchart for systematic reviews was used to present the selection process for the\nstudies.\nTitles and/or abstracts of studies obtained by the\nsearch strategy and those obtained from extra sources\nwere separated by two our team members to find\nstudies that potentially meet the aims of this study.\nThe full text of these possibly appropriate articles was\nretrieved and evaluated independently for eligibility by\nanother member of the research team. They separately\nreviewed the quality and acceptability of the articles,\nand any disputes were resolved by agreement with the\nthird members of the team.\nTo evaluate the quality of non randomized studies,\nNewcastle-Ottawa Quality Assessment Scale was used.\nThree classes of poor, moderate and good quality were\nidentified. The cut-off points included: i. obtained score\n>75%: high methodological quality with 12 stars, ii.\n50%< obtained score<75%: moderate methodological\nquality with 9-11 stars, and iii. obtained score ≤50%:\nlow methodological quality with 0-8 stars. Each study\nwas awarded a maximum of one star for each numbered\nitem within the Selection and Exposure categories. Also,\na maximum of two stars was given for Comparability.\nThe study was categorized methodologically as high\nquality, if it achieved >75% of the score ( 29 ). The\nscore of each item of the checklist was evaluated\nindependently, in duplicate, by two researchers.\nA validated data collection form was tabulated\nfor data extracted from each study. This approach\nhelped reviewers to analyze systematically. These\nextracted data for each study were composed of\nyear of publication, study population, study design,\nparticipant number, outcome measure, and summary\nof results, conclusion and quality assessment score.\nData were extracted by two authors (SM and MM),\nindependently.\nThe odds ratio (OR) (95% confidence interval [CI]) was used to express main effect size.\nBecause of the high level of heterogeneity (I 2  >75%) “random effect model\" was\nused instead of \"fixed effect model\". For heterogeneity evaluation, I 2 \nstatistic was used. Review Manager (Rev Man) version 5.3 was used for the\nmetaanalysis.\n\nThe selection process is accessible in the Figure 1. We\nfound 1905 studies of associated databases. In the first\nstep, 1405 studies were removed based on our criteria.\nIn the second step, 416 studies that did not examine the\nrelationship between the outcome variables, were omitted.\nAnd also, we miss 8 studies that did not analyze the\nassociation between sexual activity during menstruation\nand endometriosis. Finally, four studies were involved in\nthe systematic review and meta-analysis.\nCharacteristics of the included studies\nRef; Reference, n; Number of women with or without history of coitus in each group and N; Number of women in each group.\nPRIZMA Flow diagram of studies screening process.\nThe overall structure of the comprised studies were\nsummarized in the Table 1. The included studies included\ntwo cross-sectional ( 24 ,  25 ) and two case-control ( 23 ,  26 )\nstudies, which were conducted and published between\n1989 and 2019. In all studies, sexual activity during\nmenstruation, as a risk factor for endometriosis, were\nanalyzed.\nAmong these four studies, one was conducted in the\nIran by Mollazadeh et al. ( 23 ), one in Qatar by Samir\net al. ( 25 ) and two studies in the United States by Filer\nand Wu ( 24 ) and Meaddough et al. ( 26 ). The results of\nthe first three studies showed that sexual activity during\nmenstrual bleeding can increase the risk of endometriosis,\nwhile the last one, i.e. study by Meaddough et al. ( 26 )\nshowed that sexual activity may have a protective effect\non endometriosis.\nThe results of the methodological quality evaluation by\nNewcastle-Ottawa Quality Assessment Scale showed that\nboth studies by Mollazadeh et al. ( 23 ) and Meadddough et\nal. ( 26 ) were categorized in a high methodological quality\nwith 14 and 12 stars, respectively [achieved score >75%];\nwhereas Samir et al ( 25 ) and Filer and Wu ( 24 ) studies\nwere categorized in low methodological quality with 6\nand 7 stars, respectively [achieved score ≤50%].\nThe results of meta-analysis on 3641 participants (2251 cases and 1390 controls) revealed\napproximately two times higher probability of having sexual activity during menstruation in\nthe case group in comparison with the control group was (OR=1.80, 95% CI: 1.12 to 2.90,\nP=0.02). The heterogeneity was higher (I2=78%, Tau=0.17, Chi 2  =13.72, P=0.003,\n Fig .2 ).\nAssosiation between sexual activity during menstruation and\nendometriosis.\n\nEndometriosis is a problematical disease that disturbs\nthe most important aspects of reproductive age women's\nlife, such as fertility ( 19 ,  30 ,  31 ). Some studies showed\nthat the sexual activity during menstruation increase the\nrisk of endometriosis ( 23 - 25 ).\nThere are generally three theories about the\npathogenesis of endometriosis, including: i. Celomic\nmetaplasia, ii. residual embryonic Müllerian duct, iii.\nretrograde menstruation. Since retrograde menstruation\nis considered the main etiology of the endometriosis\ndevelopment, it is assumed that sexual activity during\nmenstruation may possibly rise retrograde menstruation,\nthe seed endometrial tissue in other places, and thus end to\nthe risk of endometriosis. The existing systematic review\nand meta-analysis aimed to respond the question whether\nsexual activity through menstruation can be related to the\noccurrence of endometriosis. Up to now, four studies ( 23 -\n 26 ) have studied the relationship between sexual activity\nduring menstruation and endometriosis.\nThe results of all three studies by Mollazadeh et al. ( 23 ),\nSamir et al. ( 25 ) and Filer and Wu ( 24 ) were consistent\nand showed that sexual activity during menstrual\nbleeding can increase the risk of endometriosis. They\ninferred that sexual activity during menstruation may\nrise the risk of retrograde menstrual bleeding, thereby,\nincrease the probability of seeding endometrial tissue\nin places other than the endometrial cavity, while the\nstudies showed that women who were less eager to\nhave sexual activity during menstruation were more\nlikely to develop endometriosis; So sexual activity\nmay have a protective effect on the endometriosis. This\nissue is due to misinterpretation of the results, because\nsexual activity does not have a protective effect on the\nendometriosis. Women with endometriosis are reluctant\nto have sexual activity due to pain during intercourse\n(dyspareunia). They inferred that a probable clarification\nfor these results, on the contrary, is the inadequacy of\nresearch tools or existence of confusing variables such as\ndyspareunia that were not involved in the questionnaire.\nAlso, they inferred sexual activity may cause more\neffective menstrual discharge clearance of the vaginal\nvault, which in turn may facilitate cervical outflow,\nwhich Meaddough et al. ( 26 ) have mentioned well in the\ndiscussion section of their article.\nSexual activity during menstruation is a forbidden\nIslamic behavior that has been written in the Holy Qur'an in Aya 222 of the Surat Al Baqarah: Avoid intercourse with\nmenstruated wife until the end of their period is one of\nIslam religion rules ( 32 ) . Relatively, ethical philosophies\nassociated with sexual intercourse during menstrual\nbleeding are also introduced by the fuqaha and the Shari'a.\nAll of them advise not to have sexual activity with women\nuntil their menstrual bleeding is over ( 29 ,  33 ).\nIn Christianity, similar to Islam, it is emphasized to\navoid intercourse with women during menstrual bleeding.\nJudaism has wide laws (laws of niddah or family purity)\nthat emphasize the avoidance of any sexual contact\nbetween couples during uterine bleeding ,which is not due\nto a wound or uterine injury ( 28 ).\nAvicenna in his book titled \"The Canon of Medicine\"\nhas stated that it would be better if sexual intercourse takes\nplace after a woman is cleansed of menstruation ( 34 ).\nThe strength of this systematic review was that selection\nof women with endometriosis was based on definitive\nhistological analysis of endometriosis by laparoscopy\nin all included studies. This study had also some\nlimitations; two included studies in the present review\nhad low methodological quality. Also, the method for\nassessing the sample size in three of the included studies\nwas not mentioned. Other limitation comes from more\nheterogeneous results across studies as well. For this reason,\nfurther studies with stronger designs are recommended.\n\nAccording to our results, sexual activity during\nmenstruation can be a predisposing risk factor for\nendometriosis. Proper health education for women of\nreproductive age can promote their health and also,\nprevents endometriosis. The findings of this study can be\nused as a guide for medical staff in transmitting correct\ninformation to women of childbearing age. The midwife\nconsultants , particularly, can benefit from such knowledge\nand in order to improve young girls and women‘s sexual\nhealth.","source_license":"CC0","license_restricted":false}