{"paper_id":"9a9c8220-86d2-4e35-a64a-d24e6dbab515","body_text":"Mojtahedi et al. \nMiddle East Fertility Society Journal           (2023) 28:26  \nhttps://doi.org/10.1186/s43043-023-00153-7\nRESEARCH\nThe effect of letrozole as an adjunct \nin GnRH-antagonist protocol on IVF/ICSI \noutcome in women with endometriosis: \na randomized clinical trial\nMaryam Farid Mojtahedi1, Ashraf Moini2,3*, Ladan Kashani1 and Tiba Mirzarahimi4 \nAbstract \nBackground To evaluate the effect of adding letrozole to the antagonist ovarian stimulation protocol (COS) on in-\nvitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) outcome in endometriosis patients.\nMethods This randomized clinical trial was carried out in the department of infertility treatment at Arash Women’s \nHospital from May 2019 to May 2021. The eligible women with normal ovarian reserve tests who had endometriosis \ndiagnosis and underwent IVF/ICSI cycles were evaluated. A flexible regimen of GnRH-antagonist protocol was used \nfor COS. In the experimental (n = 34), the patients received 5 mg letrozole daily for the first 5 days in combination \nwith 150 IU of recombinant follicle-stimulating hormone (rFSH). In the control group (n = 30), the patients received \nonly the same dose of rFSH. The treatment cycle was compared between groups.\nResults Analysis of demographic characteristics, severity of endometriosis, and baseline hormonal tests of patients \nshowed that the two groups were similar and comparable. The means of total used gonadotropins ampoules \nand serum  E2 level on oocyte trigger day in the letrozole group were significantly lower than those of in the con-\ntrol group (P = 0.03 and P = 0.004, respectively). No statistically significant difference in terms of the total number \nof retrieved and MII oocytes as well as the total numbers of obtained and top-quality embryos, and cryopreserved \nembryos was found.\nConclusion The co-treatment of letrozole with gonadotropins during the antagonist protocol was associated \nwith a reduction in the total dose of gonadotropins, although it had no effect on the oocyte or embryo yield \nin patients with endometriosis.\nTrial registration The study was registered in the Iranian Registry of Clinical Trials on 2018 -07-13 \n(IRCT20150310021420N4 at www. irct. ir, registered while recruiting).\nKeywords In vitro fertilization, Letrozole, An aromatase inhibitor, Live birth, Oocyte maturity\nOpen Access\n© The Author(s) 2023. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which \npermits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the \noriginal author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or \nother third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line \nto the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory \nregulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this \nlicence, visit http://creativecommons.org/licenses/by/4.0/.\nMiddle East Fertility\nSociety Journal\n*Correspondence:\nAshraf Moini\nashraf.moieni@gmail.com; a_moini@royaninstitute.org\nFull list of author information is available at the end of the article\n\nPage 2 of 8Mojtahedi et al. Middle East Fertility Society Journal           (2023) 28:26 \nBackground\nIn recent years, one of the most important goals of \nassisted reproductive cycles (ART) in women is to focus \non optimizing the method of ovarian stimulation with \nthe least destructive effect on the endometrium. Individ -\nualization of ovarian stimulation protocol based on the \npatient’s age, ovarian reserve tests, the cause of infertility, \nand the previous treatment history can allow for a safer \nand more effective ART practice [1]. One of the causes of \ninfertility that has been reported to have negative effects \non both the ovaries and the endometrium is the diagno -\nsis of endometriosis. It can be associated with ovulation \ndisorders and decreased oocyte quality due to adverse \nchanges in the process of folliculogenesis and steroido -\ngenesis of granulosa cells as well as low-quality embryos, \ndecreased implantation rate, sperm phagocytosis, and \ntoxic environment for fetus due to pelvic adhesions in \nadvanced stages [2–5]. It is important to select an appro -\npriate ovarian stimulation protocol for these patients, \nwhich in turn improves endometrial receptivity.\nA type of hormonal manipulation involves the use of \naromatase inhibitors (AIs) along with COH standard \nprotocol [6]. The aromatase p450 is a key enzyme in the \nbiosynthesis of estradiol  (E2) by ovarian granulosa cells in \npremenopausal time, whose expression in both eutopic \nand ectopic endometrial tissue in patients with endome -\ntriosis is significantly higher than in non-endometriosis \nwomen [7]. Abnormal expression of aromatase leads to \nthe production of estrogen locally at the site of implan -\ntation of ectopic endometrial cells. Since endometriosis \nis an estrogen-dependent disease, AIs appear to be good \ncandidates for the treatment of endometriosis [7–10]. \nThe third generation of Als, mainly letrozole (LZ) is a \nselective and non-steroidal AI which is superior to clo -\nmiphene citrate for ovulation induction in patients with \npolycystic ovary syndrome [11]. Lu et  al. in  vivo study \nshowed that LZ significantly reduces  E2 production and \naromatase p450 gene expression in luteinized granulosa \ncells belonging to women with advanced stages of endo -\nmetriosis [12].\nRecently, the beneficial effects of adjuvant therapy \nwith LZ in GnRH antagonist-controlled ovarian stimu -\nlation (COS) protocol have been reported in patients \nwith poor ovarian response [13, 14]. Some studies have \nshown favorable effects of AIs in the treatment and pre -\nvention of recurrence of pain and other complications of \nendometriosis [15]. Furthermore, Miller et  al. proposed \nthis hypothesis that lack of endometrial ανβ3 integrin \nexpression is associated with a poor prognosis for IVF in \nendometriosis patients that might be improved with LZ \nco-treatment [16]. Only one retrospective study has eval -\nuated the use of LZ in combination with gonadotropin on \nIVF outcomes in endometriosis patients and concluded \nthat the combination therapy with LZ and gonadotropin \nproduces similar oocyte and embryo yield to the conven -\ntional IVF protocol in women with endometriosis [16].\nSince the use of AIs for improvement of infertility \ntreatment in women with endometriosis is an interesting \nsubject and clinical trial studies are still necessary for this \narea, The researchers designed a randomized clinical trial \nto evaluate the effect of adding LZ to the antagonist ovar-\nian stimulation protocol on IVF outcome in endometrio -\nsis patients.\nMethods\nThis randomized clinical trial (RCT) was carried out in \nthe department of infertility treatment in Arash Wom -\nen’s Hospital from May 2018 to May 2021. The women \nin the age range of 18 to 42 years old with endometriosis \ndiagnosis who underwent in  vitro fertilization/intracy -\ntoplasmic sperm injection (IVF/ICSI) cycles were evalu -\nated. Endometriosis diagnosis was defined according to \nsonographic evaluation by two experienced sonographers \nor the pathologic result of the previous laparoscopy. \nEndometriosis staging is done according to Enzian clas -\nsification by sonographic features (TVS and endo-anal \nultrasound) done by 2 expert radiologists) [17, 18].\nThe patients with body mass index > 25  kg/m2, dimin-\nished ovarian reserve (i.e., antral follicle count (AFC) < 5 \nfollicles or anti-Mȕllerian hormone (AMH) < 1.1 ng/ml), \ndonor/recipient or surrogacy treatments, metabolic, or \nendocrine disorders including (diabetes, hypo/hyperthy -\nroidism, hyperprolactinemia, hypothalamic amenorrhea, \netc.), immunologic diseases (lupus, rheumatoid arthri -\ntis, antiphospholipid syndrome, cardiovascular, liver and \nkidney disease), congenital uterine anomalies and endo -\nmetrial cavity disorders (Asherman syndrome, myoma, \npolyps, etc.), recurrent IVF failures (more than three \nconsecutive failures and azoospermic male partner were \nnot included in the study.\nThe eligible patients on 2nd or 3rd day of the menstrual \ncycle were allocated into two groups randomly by strati -\nfied (based on the polycystic ovary syndrome (PCOS) \ndiagnosis) block randomization method. The random \nallocation list for patients was solely available to the epi -\ndemiologist and the number of blocks was considered 6. \nThe type of study group was written on 72 cards, respec -\ntively, and then placed inside sealed envelopes. When \nthe physician announced the eligibility of a patient, the \nmethodologist provided the doctor with the envelope. \nThe random allocation process and type of intervention \nwere concealed from the assessor of the final outcome \nand also the data analyzer.\nThe same controlled ovarian stimulation protocol (a \nflexible regimen of GnRH-antagonist) was used for all \nstudy populations. The ovarian quiescence was confirmed \n\nPage 3 of 8\nMojtahedi et al. Middle East Fertility Society Journal           (2023) 28:26 \n \nby documenting the absence of ovarian cyst or lead folli -\ncle > 10 mm and the serum  E2 concentrations < 50 pg/mL \nthrough baseline ultrasounds and hormonal assessment \nwhich were performed on the 2nd or 3rd day of the men -\nstrual cycle. In the experimental (LZ group), the patients \nreceived 5  mg LZ (Letrofem ®; Iran hormone, Tehran, \nIran) for the first 5  days of ovarian stimulation with \n150 IU of recombinant human FSH (Cinnal-f, Cinagen), \nIn the control group, the patients received only 150  IU \nof rFSH. The follicular maturation monitoring was done \nby serial vaginal ultrasound (sonographic device: Phil -\nlips, affinity 70) assessments. According to the ovarian \nresponse in each patient, the dosage of gonadotropins \nwas adjusted. The administration of GnRH antagonist \n(Cetrotide ®, Serono International, Geneva, Switzer -\nland) (0.25  mg/day subcutaneously) was initiated when \nfollicle(s) ≥ 13  mm in average diameter were observed, \nand it was continued until the day of final oocyte trig -\ngering. When at least two follicles measuring ≥ 18 mm in \ndiameter were observed, the final stage of oocyte matu -\nration was induced by two doses of recombinant hCG \n(250  μg) (Ovitrelle; Merck Serono). Transvaginal ultra -\nsound-guided oocyte retrieval was performed 34–36  h \nafter final oocyte triggering. The serum levels of estradiol \nand progesterone were measured on the day of oocyte \ntrigger and if the amount of progesterone was more than \n1 ng/ml, the plan for freezing all the embryos was made.\nIn vitro fertilization and/or intracytoplasmic sperm \ninjection (IVF/ICSI) was performed with ejaculated \nsperm to metaphase II (MII) oocytes through standard \nprocedure. The obtained Embryos were cultured in a \ncommercially available culture medium until the day of \ntransfer. Embryo quality was determined according to \nthe number and regularity of blastomeres and the degree \nof embryonic fragmentation. Two or 3 days after oocyte \nretrieval, a maximum of two good-quality embryos at the \ncleavage stage were transferred under ultrasound scan \nguidance by a catheter (Guardia ™, Access ET Catheter, \nCook Medical). The luteal phase was supported by 400 \nmg vaginal progesterone suppository twice daily (Cyc -\nlogest, Actavis, Barnstaple, UK) starting on the evening \nof the oocyte retrieval and it was continued for 10 weeks \nin cases with a positive pregnancy test. A serum ß-hCG \nanalysis was done 14  days after the ET, and the clinical \npregnancy (presence of gestational sac with heartbeat) \nwas documented by ultrasound scan four weeks later. \nOngoing pregnancy was considered when the pregnancy \nwas continued over 20 weeks of gestation.\nStatistical analysis\nThe primary outcomes in the present study were the \nnumber of oocytes retrieved, the number of MII oocytes, \ntotal number and quality of obtained embryos. The \nsecondary outcomes were clinical pregnancy and live \nbirth rates. The Statistical Package for the Social Sci -\nences, version 22, SPSS Inc, Chicago, IL, USA (SPSS) \nwas used for the statistical analysis. The Kolmogorov–\nSmirnov test was applied to detect the normality of \nquantitative variables and it was determined that all of \nthese variables had normal distribution. The independ -\nent Student t-test and chi-square test were used for the \ncomparison of the quantitative and qualitative variables \nbetween groups respectively. The descriptive data were \npresented as mean ± standard deviation (SD) or number \n(percent). The statistical significance level was considered \nas p value < 0.05. The sample size was estimated based on \nKim et al. (a retrospective study) using NCSS-PASS soft -\nware (version 2007; NCSS Inc., Kaysville, UT, USA) and \nit was determined that 70 subjects were needed in each \nstudy group considering α = 0.05, and 80% power. How -\never, in the sampling process, we found that the number \nof patients with a diagnosis of endometriosis who have \na normal ovarian reserve and consented to participate \nin the study was very limited. Due to the long duration \nof the project, it was decided to end the study; since this \nstudy is one of the first RCTs in patients diagnosed with \nendometriosis, it can be reported as a pilot with a mini -\nmum sample size according to Julious’s study [19].\nResults\nAmong 124 women who were screened during the study \nperiod, 70 were eligible and enrolled in the study after \nobtaining their informed consent (35 patients in each \ngroup), after follow-up finally the result of treatment \ncycles were compared between groups (Fig.  1). The base-\nline characteristics and hormonal profiles of the patients \nare illustrated in Table  1. The analysis showed that there \nwas no significant difference in terms of women’s age and \nBMI, duration and type of infertility, PCOS diagnosis, \nand AFC as well as basal serum levels of LH and FSH, \nserum AMH and, TSH between groups. There was no \nsignificant difference in the type and severity of endome -\ntriosis between groups (P = 0.528 and P = 0.405).\nThe outcomes of the ovarian stimulation cycle are com-\npared between groups in Table 2. The means of total used \ngonadotropins ampoules and serum  E2 level on oocyte \ntrigger day in the LZ group were significantly lower than \nthat of the control group (P = 0.03 and P = 0.004, respec-\ntively); however, the duration of ovarian stimulation was \nsimilar in two groups (P = 0.58). The analysis indicated \nthat the two groups had no statistically significant differ -\nence in terms of the number of follicles with 14–17 mm \nin diameter at trigger, total number of retrieved and MII \noocytes as well as total number of obtained embryos, \nnumber of top-quality and total number of cryopreserved \nembryos.\n\nPage 4 of 8Mojtahedi et al. Middle East Fertility Society Journal           (2023) 28:26 \nIn the following, the number of cases with fresh and \nfrozen embryo transfers was comparable between \ngroups. It is worth noting that 10 (29.4%) cases of the \npatients in the intervention group and 9 (30%) patients \nin the control group had not been referred for the frozen \nembryo transfer until the manuscript preparation time.\nDiscussion\nThe use of LZ as an adjunct in GnRH-antagonist ovarian \nstimulation protocol for infertile women with endome -\ntriosis was associated with a significantly lower dosage of \nadministrated gonadotropins compared with the stand -\nard GnRH-antagonist protocol. The trend toward \nimprovement in the total number of retrieved and meta -\nphase II oocytes as well as the total number of obtained \nembryos was observed in the LZ group; however, it was \nnot statistically significant. Interestingly, in the follow-\nup after ET, the clinical pregnancy rate was significantly \nhigher than the control group.\nUntil now, some studies have been designed and con -\nducted to investigate the effect of LZ as an adjunc -\ntive treatment in the COS protocol in patients with \npoor ovarian [11, 13, 20–24], normal [25, 26], and high \nresponses [27] as well as in patients with breast cancer \nfor fertility preservation [28]. The reported results in var-\nious studies have been conflicting. Bülow et al. in a meta-\nanalysis study concluded that co-administration of LZ in \nIVF cycles in patients with a poor ovarian response may \nbe associated with improved outcomes; however, studies \nregarding normal patients or high responders are lim -\nited, and further randomized clinical trials are required \nin this field [29]. The LZ increases ovarian response to \nstimulation protocol through mediation in reducing \nserum estrogen levels and temporary rising in intraovar -\nian androgen concentrations that cause prolongation of \nthe follicular phase, enhance the affinity of FSH recep -\ntors, preantral and antral follicle growth [30, 31]. Besides, \nthe reduced serum  E2 concentration attributed to LZ \nmay justify the negative impact of excessive  E2 levels on \nFig. 1 Flowchart of the study sampling\n\nPage 5 of 8\nMojtahedi et al. Middle East Fertility Society Journal           (2023) 28:26 \n \noocyte quality and endometrial receptivity in ART cycles \n[21]. In line with the results of the present study, Eft -\nekhar et al., in a clinical trial reported that co-treatment \nof LZ with gonadotropins reduced the total amount of \nconsumed gonadotropin in patients with normal ovar -\nian reserve; however, it did not improve the pregnancy \nTable 1 Demographic and clinical characteristics of study participants in two groups\nTSH thyroid-stimulating hormone, AMH anti-Müllerian hormone, OMA ovarian endometriosis, DIE deep infiltrating endometriosis\nDescriptive data were compared using independent Student’s t-test and presented as mean ± SD. P value ≤ 0.05 was considered statistically significant. No. number, \nFSH follicle-stimulating hormone, LH luteinizing hormone\nVariables Letrozole group (N = 34) Control group (N = 30) P value\nFemale age (years) 31.38 ± 5.06 33.41 ± 4.51 0.10\nBody mass index (kg/m2) 21.9 ± 2.2 21.5 ± 2.4 0.56\nDuration of infertility (years) 2.2 ± 2.34 3.7 ± 3.5 0.06\nNo. of couples with primary infertility, n (%) 28 (82.4) 22 (73.3) 0.65\nNo. of women with dysmenorrhea, n (%) 17 (50) 16 (53.3) 0.78\nPCOS diagnosis, n (%) 5 (14.7) 4 (13.3) 0.91\nEndometriosis type, n (%)\n OMA 24 (52.9) 23 (76.7) 0.528\n DIE 10 (47.1) 7 (23.3)\nEndometriosis stage, n (%)\n Stage III 29 (85.3) 28 (93.3) 0.405\n Stage IV 5 (14.7) 2 (6.7)\nBasal serum level of FSH (IU/L) 4.0 ± 2.2 4.9 ± 2.4 0.13\nBasal serum level of LH (IU/L) 4.5 ± 2.3 5.4 ± 2.2 0.11\nSerum level of AMH (ng/ml) 2.4 ± 1.1 2.1 ± 1.5 0.31\nSerum level of TSH (IU/mL) 1.3 ± 1.3 1.5 ± 1.1 0.52\nAntral follicle count 7.3 ± 2.1 6.9 ± 3.1 0.43\nNo. of previous failed IVF cycles 0.14 ± 0.34 0.41 ± 0.73 0.10\nTable 2 Comparison of stimulation and cycle outcomes in the two study groups\nDescriptive data were compared using an independent Student’s t-test and presented as mean ± SD. P value ≤ 0.05 was considered statistically significant. No.: number\na 10 (29.4%) cases of the patients in the intervention group and 9 (30%) patients in the control group had not been transferred the frozen embryos until the \nmanuscript preparation time\nVariables Letrozole group (N = 34) Control group (N = 30) P value\nTotal gonadotropins ampoules (75 IU) 28.4 ± 8.5 34.3 ± 12.6 0.03\nDuration of stimulation (day) 10.8 ± 1.9 11.2 ± 2.5 0.58\nEstradiol level on trigger day (pg/ml) 1837.5 ± 577.6 2283.7 ± 606.4 0.004\nNo. of follicles with 14–17 mm in diameter at trigger 2.4 ± 2.1 2.8 ± 2.3 0.48\nNo. of follicles > 17 mm in diameter at trigger 2.7 ± 1.2 2.2 ± 0.74 0.11\nNo. of retrieved oocytes 11.5 ± 8.9 8.2 ± 7.7 0.12\nNo. of metaphase II oocytes 8.4 ± 7.1 6.5 ± 6.3 0.29\nNo. of obtained embryos 4.4 ± 2.6 4.0 ± 3.4 0.63\nNo. of top-quality embryo 3.1 ± 2.3 2.8 ± 2.8 0.62\nNo. of cryopreserved embryos 4.0 ± 3.0 3.6 ± 3.7 0.61\nNo. of all freeze cases, n (%) 30 (88.2) 28 (93.3) 0.84\nNo. of cases with fresh embryos transferred, n (%) 4 (11.8) 2 (6.7) 0.80\nChemical pregnancy rate/total ET (%) 12/ 24 (50) 3/21 (14.3) 0.01\nClinical pregnancy/total  ETa (%) 10/24 (41.6) 3/21 (14.3) 0.04\nMiscarriage rate/total ET (%) 2/24 (8.3) 0/0 0.39\nLive birth rate/total ET 8/24 (33.8) 3/21 (14.3) 0.12\n\nPage 6 of 8Mojtahedi et al. Middle East Fertility Society Journal           (2023) 28:26 \noutcomes [25]. In a similar way, Haas et al. demonstrated \nthat co-treatment with LZ improves the IVF outcome \nin normal responders in terms of the increased number \nof obtained blastocysts without changing the pregnancy \nrate or the risk of OHSS [26]. Elsewhere, et al., reported \nthat total dose of administrated rFSH and risk of OHSS \nwere significantly decreased in patients with male factor \ninfertility who received LZ as an adjunct to gonadotro -\npins. Furthermore, Yang and colleagues in a pilot RCT, \nconcluded that LZ supplementation could not reduce \nthe incidence of the premature rising of progesterone \nduring the late follicular phase in patients with expected \nhigh ovarian response to standard stimulated IVF cycles, \nwhich was associated with producing a harmful effect on \nthe pregnancy outcome. Finally, Bülow et al., in a multi -\ncenter double-blinded RCT evaluated 129 women with \nexpected normal ovarian reserve to this question of \nwhether LZ supplementation during COS with gonado -\ntropins for IVF reduces the proportion of women with \npremature progesterone levels above 1.5  ng/ml at the \ntime of final oocyte maturation triggering?. The results \nof their study showed that although the use of LZ has no \nimpact on the proportion of women with a premature \nrise in progesterone on the day of oocyte triggering, the \nincreased progesterone in the mid-luteal phase due to LZ \nmay contribute to optimizing the luteal phase endocri -\nnology [32]. The effect of LZ on increasing androgens and \nreducing gonadotropin consumption might be applied \nin poor responders. It was concluded that the impact of \nLZ on implantation and pregnancy outcomes should be \nassessed in a meta-analysis or larger RCT [32].\nBased on our knowledge, the studies that are specific \nto patients diagnosed with endometriosis are limited. \nRecently, Kim et al., in a retrospective study, compared \nIVF outcomes of 38 patients who received standard \nCOS protocol along with co-treatment of LZ versus \n26 patients with standard COS protocol alone. It was \nconcluded that the combination therapy with LZ and \ngonadotropin was associated with a significantly lower \npeak estradiol level and similar oocyte and embryo \nyield to the conventional IVF protocol in endometriosis \npatients [16]. In agreement with their study, we also did \nnot find a positive effect of LZ on the number and qual -\nity of oocytes and embryos. Although in the follow-up \nof pregnancies in the LZ group, the clinical pregnancy \nrate per total embryos transferred cycles was higher \nthan the control group, due to the fact that the major -\nity of embryo transfers were of the frozen type, we \ncould not comment regarding the effect of LZ on the \nimplantation and pregnancy rates. Based on the results \nobtained from previous studies in patients with dif -\nferent causes of infertility, it is likely that LZ through \nthe mentioned mechanisms can have a positive effect \non reducing the duration of stimulation or the total \ndose of consumed gonadotropin and in some cases has \naccompanied by increasing the number of MII oocytes \nand/or high quality of embryos. However, the conclu -\nsion about its effect on the pregnancy rate requires \nRCT studies with larger sample sizes.\nThe study has a strong point in that it is designed as \na randomized clinical trial. The present study had limi -\ntations that should be mentioned, considering that the \neligible population had a low prevalence, the number \nof subjects collected in the time frame considered for \nthe study was less than the estimated sample size, so \nthe study was terminated as a pilot trial. On the other \nhand, the number of cases of all-freeze embryos in \nboth groups was high due to various reasons, including \nOHSS at risk, the spread of COVID-19 disease, or the \npersonal preference of the patients, so we have no data \nto report about the effect of letrozole on the implanta -\ntion rate in fresh embryo transfer cycles. We suggest \nthat future studies be designed with the primary aim \nof investigating the rates of implantation and clinical \npregnancy in patients with endometriosis.\nThe current pilot study indicated that the co-treat -\nment of letrozole with gonadotropins during the antag -\nonist protocol was associated with a reduction in the \ntotal dose of gonadotropins, although it had no effect \non the oocyte or embryo yield, more studies are nec -\nessary to determine its impact on the rate of implan -\ntation in fresh embryo transfer cycles in patients with \nendometriosis.\nAbbreviations\nART   Assisted reproduction technologies\nAMH  Anti-müllerian hormone\nAIs  Aromatase inhibitors\nCOS  Ovarian stimulation protocol\nE2:  Estradiol\nFSH  Follicle stimulating hormone\nGnRH  Gonadotropin-releasing hormone\nhCG  Human chorionic gonadotropin\nIVF  In-vitro fertilization\nICSI  Intracytoplasmic sperm injection\nLZ  Letrozole\nRCT   Randomized clinical trial\nLH  Luteinizing hormone\nSD  Standard deviation\nAcknowledgements\nWe would like to thank all the participants and co-workers at Arash Women’s \nHospital for their assistance in this study.\nAuthors’ contributions\nM.FM. and A.M. designed the research. M.FM and L.K. contributed to patient \nselection, data collection, interpretation of data, and manuscript editing. A.M. \nand M.FM wrote the manuscript. T.M. assisted in the analysis of the data. All \nauthors read and approved the final manuscript.\nFunding\nThe study did not have any funding support.\n\nPage 7 of 8\nMojtahedi et al. Middle East Fertility Society Journal           (2023) 28:26 \n \nAvailability of data and materials\nThe datasets used or analyzed during the current study are available from the \ncorresponding authors on reasonable request.\nDeclarations\nEthics approval and consent to participate\nThe Institutional Review Boards and the Ethics Committees of Tehran \nUniversity of Medical Sciences approved this study (approval code: IR.TUMS.\nMEDICINE.REC.1398.186). All procedures performed in studies involving \nhuman participants were in accordance with the ethical standards of the 1964 \nHelsinki Declaration and its later amendments. The eligible patients signed \nwritten informed consent forms prior to participation in the study.\nConsent for publication\nNot applicable.\nCompeting interests\nThe authors declare that they have no competing interests.\nAuthor details\n1 Department of Gynecology and Obstetrics, Infertility Ward, Arash Women’s \nHospital, Tehran University of Medical Sciences, Tehran, Iran. 2 Breast Disease \nResearch Center (BDRC), Tehran University of Medical Sciences, Tehran, Iran. \n3 Department of Endocrinology and Female Infertility, Reproductive Biomedi-\ncine Research Center, Royan Institute for Reproductive Biomedicine, ACECR, \nTehran, Iran. 4 Department of Obstetrics and Gynecology, Alavi Hospital, \nArdabil University of Medical Sciences, Ardabil, Iran. \nReceived: 14 December 2022   Accepted: 17 October 2023\nReferences\n 1. La Marca A, Sunkara SK (2014) Individualization of controlled ovarian \nstimulation in IVF using ovarian reserve markers: from theory to prac-\ntice. 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