Ovulation Induction In Patients Research Articles

Comparison of the Effect of Letrozole Alone With Letrozole Plus N-Acetylcysteine on Pregnancy Rate in Patients With Polycystic Ovarian Syndrome: A Randomized Clinical Trial

Objectives: Different drugs are prescribed for the induction of ovulation in patients with polycystic ovary syndrome (PCOS). The aim of this study was to compare the effect of letrozole alone with letrozole plus N-acetyl cysteine (NAC) on the pregnancy rate in patients with PCOS. Materials and Methods: This clinical trial studyincluded317 patients with PCOS in the infertility clinic of Zahedan in 2018. Patients were randomly divided into letrozole and NAC plus letrozole groups. Then, several parameters were evaluated in both groups, including the pregnancy rate, number of follicles larger than 18 mm, endometrial thickness, and the endometrial pattern. Finally, data were analyzed using SPSS 25, and t-test and chi-square tests were used for statistical analysis. Results: The mean age of study participants was 28.5 ± 4.9 years old. The mean duration of infertility in the intervention group was 4.5 ± 3.8 years. The mean anti-MA¼llerian hormone and the mean endometrial thickness of patients in the intervention group were 4.4± 3.6 ng/mL and 7.6 ± 2.5 mm, respectively. Eventually, the pregnancy rate was 14.6 (n = 23) and 7.5 (n = 12) in the intervention and control groups, respectively (P = 0.046). Conclusions: The results of this search revealed that the number of follicles with the size of 18 mm in the control group was higher compared to the intervention group, but the fertility rate in patients with PCOS receiving letrozole plus N-acetylcysteine was significantly higher. © 2021 The Author(s);.

Letrozole Therapy versus Extended Clomiphene Citrate Therapy for Induction of Ovulation in Resistant Patients with Polycystic Ovarian Syndrome in Low Resource Communities

Background: many drugs can be used in ovulation induction in patients with clomiphene-resistant polycystic ovarian syndrome (PCOs). Objective: to evaluate the effect of letrozole therapy versus extended clomiphene citrate therapy for ovulation induction in clomiphene-resistant polycystic ovarian syndrome patients Patients and Methods: The study included 100 infertile patients who had failed induction by clomiphene for three cycles. They were randomly allocated to receive either letrozole or extended clomiphene therapy. The effects of these drugs on follicular volume, ovulation, endometrium thickness and occurrence of pregnancy were evaluated. Results: No significant difference was found between both groups regarding age, body mass index, basal FSH level, LH level, prolactin level, thyroid function and semen analysis of the husband. Use of letrozole or extended clomiphene led to improvement of number of growing follicles, ovulation rate and pregnancy rate after 3 cycles of ovulation induction. Conclusion: The results of this study revealed that use of letrozole or extended treatment with clomiphene did not show better outcomes over each other in number of growing follicles, ovulation rates, occurrence of pregnancy and pregnancy outcomes. Letrozole group showed a significant increase in the endometrium thickness than extended clomiphene group but this did not affect pregnancy rate.

Letrozole Therapy versus Extended Clomiphene Citrate Therapy for Induction of Ovulation in Resistant Patients with Polycystic Ovarian Syndrome in Low Resource Communities

Background: many drugs can be used in ovulation induction in patients with clomiphene-resistant polycystic ovarian syndrome (PCOs). Objective: to evaluate the effect of letrozole therapy versus extended clomiphene citrate therapy for ovulation induction in clomiphene-resistant polycystic ovarian syndrome patients Patients and Methods: The study included 100 infertile patients who had failed induction by clomiphene for three cycles. They were randomly allocated to receive either letrozole or extended clomiphene therapy. The effects of these drugs on follicular volume, ovulation, endometrium thickness and occurrence of pregnancy were evaluated. Results: No significant difference was found between both groups regarding age, body mass index, basal FSH level, LH level, prolactin level, thyroid function and semen analysis of the husband. Use of letrozole or extended clomiphene led to improvement of number of growing follicles, ovulation rate and pregnancy rate after 3 cycles of ovulation induction. Conclusion: The results of this study revealed that use of letrozole or extended treatment with clomiphene did not show better outcomes over each other in number of growing follicles, ovulation rates, occurrence of pregnancy and pregnancy outcomes. Letrozole group showed a significant increase in the endometrium thickness than extended clomiphene group but this did not affect pregnancy rate.

Malignant Ovarian Dysgerminoma Following Ovulation Induction in Patients with Polycystic Ovarian Syndrome: A Literature Review and Two Case Reports

Background: The relation of ovarian induction drugs to development of ovarian cancer is still unclear. Polycystic ovary syndrome (PCOS) is a complex endocrine disorder that has been reported as a risk factor for ovarian cancer in some studies. Case presentation: We report two cases with polycystic ovarian syndrome who developed a malignant ovarian dysgerminoma following use of ovulation induction drugs. One of them was diagnosed during fifth month of pregnancy by intracytoplasmic injection (ICSI). Both cases were treated with conservative surgery. Conclusion: We reported 2 cases of ovarian dysgerminoma in patients with PCOS following ovarian stimulation. A large multicenter observational study is recommended to investigate a possible association.

A randomized clinical trial of sildenafil plus clomiphene citrate to improve the success rate of ovulation induction in patients with unexplained infertility.

To investigate the role of sildenafil citrate in improving ovulation induction success rate in women with unexplained infertility. A randomized clinical trial from January to December 2018 of 80 women with unexplained infertility randomized into two groups. Both groups received 100mg clomiphene citrate once daily from days 3-7 of the menstrual cycle. The study group also received 25mg oral sildenafil citrate twice daily from days 8-12 of the same cycle. Transvaginal ultrasound assessed ovulation, endometrial thickness, and number of follicles. Pregnancy was assessed 2weeks after ovulation. Primary outcome measures were endometrial thickness, number of mature follicles, and pregnancy rates. Pregnancy rates (26 (65%) and 16 (40%), P=0.043) and endometrial thickness (10.4±1.4 and 9.2±1.9, P=0.007) were significantly higher in the study group. More women in the study group reported adverse effects compared with the control group (17 [42.5%] vs 9 [22.5%]; P=0.034), with headache the most common adverse effect in the study group, reported by 8 (20.0%) patients. Adding sildenafil citrate improved ovulation success rate and increased pregnancy rate. PACTR201907658492123.

Levothyroxine with Clomiphene Citrate for Ovulation Induction in Patients with Polycystic Ovary Syndrome and Subclinical Hypothyroidism

Levothyroxine with Clomiphene Citrate for Ovulation Induction in Patients with Polycystic Ovary Syndrome and Subclinical Hypothyroidism

Letrozole is superior to clomiphene citrate in ovulation induction in patients with polycystic ovary syndrome.

Objective:This study was aimed to compare the clinical outcomes of ovulation induction (OI) by timed intercourse with letrozole (LTZ) and clomiphene citrate (CC).Methods:Three hundred and twenty-three patients with polycystic ovary syndrome (PCOS) who underwent OI with LTZ or CC between February 2017 and November 2018 were included in this retrospective study. The patients were divided into two groups as the CC group (n=148) and the LTZ group (n=175). Endometrial thickness, follicular development, ovulation, clinical pregnancy, abortion, and live birth rates of the groups were analyzed.Results:The mean endometrium thickness of the CC group was 7.1±1.7 mm, and the LTZ group was 8.6±1.8 mm (p<0.001). The ovulation rate per cycle was higher in the LTZ group (93.1%) in comparison with the CC group (83.8%) (p=0.013). Clinical pregnancy rates were 52% in the LTZ group, and 41.2% in the CC group (p=0.047). LTZ with 44% of live birth rate was superior to CC with a 33% live birth rate (p=0.029).Conclusions:LTZ is an effective OI agent in PCOS patients. LTZ is superior to CC in terms of pregnancy rates and live birth rates. As a result, we recommend that LTZ should be the first-line treatment agent in patients with PCOS.

Letrozole or Clomiphene Citrate for Induction of Ovulation in Patients with Polycystic Ovarian Syndrome: A Prospective Randomized Trial

Polycystic Ovarian Syndrome (PCOS) is the most common endocrine disorder responsible for subfertility in young women. The aim of the study was to compare the efficacy of Letrozole over Clomiphene citrate (CC) for ovulation induction in patients with PCOS. It was a prospective randomized trial in a private practice setting. The study period was 3 years, which includes 240 sub fertile patients with PCOS. Patients were divided into two groups. Group-A: 120 patients got Letrozole (2.5 mg) tab, 2 tabs once daily from D2-D6 for 3 cycles. Group-B: 120 patients took tab. Clomiphene citrate (50mg), 2 tabs once daily from D2-D6 for 3 cycles. Trans-vaginal ultrasound was done on D12-D13 to document number of follicles, measurement of dominant follicle and endometrial thickness. Ovulation and pregnancy rate was measured. Results showed that Letrozole have significantly better effect on endometrial thickness (Let 9.2 mm vs CC 8.1mm) and pregnancy rate (Let 44% vs CC 24%). In CC, multiple follicles were found (CC 44% vs Let 30%). Ovulation occurred in 65% with Letrozole group and 64% in CC group without a significant statistical difference. The study concluded that Letrozole have better effect for induction of ovulation in PCOS patient in comparison to CC. Faridpur Med. Coll. J. Jul 2018;13(2): 78-81

Reprint of: Use of an aromatase inhibitor for induction of ovulation in patients with an inadequate response to clomiphene citrate

View Large Image Figure ViewerDownload Hi-res image Download (PPT)View Large Image Figure ViewerDownload Hi-res image Download (PPT)View Large Image Figure ViewerDownload Hi-res image Download (PPT)View Large Image Figure ViewerDownload Hi-res image Download (PPT) Use of an aromatase inhibitor for induction of ovulation in patients with an inadequate response to clomiphene citrateFertility and SterilityVol. 75Issue 2PreviewObjective: To use aromatase inhibition for induction of ovulation in women in whom clomiphene citrate (CC) treatment was unsuccessful. Design: Prospective trial in infertility patients treated with CC. Setting: Two tertiary-referral infertility clinics associated with the Division of Reproductive Sciences, University of Toronto. Patient(s): Twelve patients with anovulatory polycystic ovary syndrome (PCOS) and 10 patients with ovulatory infertility, all of whom had previously received CC with an inadequate outcome (no ovulation and/or endometrial thickness of ≤0.5 cm). Full-Text PDF 25 historic papers: an ASRM 75th birthday gift from Fertility and SterilityFertility and SterilityVol. 112Issue 4PreviewCraig Niederberger, M.D. Full-Text PDF

A romatase enzyme inhibitor versus gonadotropin for induction of ovulation in patients with polycystic ovary syndrome resistant to clomiphene citrate a randomized controlled trial

A romatase enzyme inhibitor versus gonadotropin for induction of ovulation in patients with polycystic ovary syndrome resistant to clomiphene citrate a randomized controlled trial

Letrezole or clomide for ovulation induction in patients with unexplained infertility.

Letrezole or clomide for ovulation induction in patients with unexplained infertility.

A Multicenter, Randomized, Equivalence Trial of a New Recombinant Human Chorionic Gonadotropin Preparation versus Ovitrelle® for Ovulation in Women Undergoing Intrauterine Insemination Following Ovarian Stimulation.

Context:A new indigenous recombinant human chorionic gonadotropin (r-hCG) has been developed in India with a comparable pharmacological profile to that of Ovitrelle® (Merck Serono).Aims:This study aims to compare the efficacy and safety of the new r-hCG with that of Ovitrelle for induction of ovulation in women undergoing intrauterine insemination (IUI).Settings and Design:Randomized (2:1), multicenter, open-label, equivalence clinical trial conducted in India.Subjects and Methods:A total of 217 women, aged 20–37 years, undergoing IUI were administered the new r-hCG (test) 250 mcg or Ovitrelle 250 mcg (comparator) after ovarian stimulation with gonadotropins. The ovulation rate was compared as the primary outcome. In addition, pregnancy rates, incidence of adverse events (AEs), and development of immunogenicity were assessed. Statistical Analysis Used: The ovulation and pregnancy rates were compared using Chi-squared test with statistical significance at P < 0.05.Results:With 144 women in the test group and 73 in the comparator group, the ovulation rate (85.4% vs. 78.1%; P = 0.17) and pregnancy rate (serum β hCG test) (11.8% vs. 12.3%; P = 0.91) were similar in both groups. A total of 15 AEs were reported (11 in the test r-hCG group and 4 in the comparator group) in 11 women; none of these were serious, and all were judged to be unrelated to the study drug. No subject developed immunogenic reaction to the test drug.Conclusions:The new preparation of r-hCG was equivalent to the conventional preparation of r-HCG in the induction of ovulation in patients undergoing IUI.

Simultaneous Letrozole and Clomiphene Citrate versus Letrozole Alone in Clomiphene Citrate Resistant Polycystic Ovary Syndrome: A Randomised Controlled Trial

Background: Polycystic ovary syndrome (PCOS) is a common cause of anovulatory infertility. The therapeutic strategies for clomiphene citrate (CC)- resistant patients include the addition of corticosteroids, extended duration of clomiphene, gonadotrophin therapy, laparoscopic ovarian drilling, in vitro fertilization or the use of aromatase inhibitors recently. Letrozole decreases estrogen levels in the body, so it releases the hypothalamus and/or pituitary gland from the negative feedback of estrogen. This increases levels of gonadotrophins, which stimulates follicular growth. Objectives: To evaluate the role of letrozole alone and simultaneous use of letrozole and clomiphene citrate (CC) for ovulation induction in patients with clomiphene citrate-resistant PCOS (CCR-PCOS). Patients and Methods: This open-label randomised controlled study was conducted in the Department of Obstetrics and Gynecology, Faculty of Medicine, Zagazig University, Egypt during the period from February 2018 to June 2019. The study included 60 CCR-PCOS patients who were randomly allocated by independent personnel into two arms: group A (letrozole alone) or B (letrozole + CC). In either group, monitoring the mean follicular diameter and endometrial thickness in the days 10, 12, and 14 of the cycle by transvaginal ultrasound and Measurement of serum Progesterone (ng/ml) 7 days after the expected time of ovulation. Results: We investigated various clinical and sonographic factors that may predict the outcome of the method of induction of ovulation in CCR-PCOS with no significant affection for the results. There was a non-significant difference between the studied groups regarding ovulation and pregnancy per cycle or per patient. Conclusion: Letrozole alone or simultaneous use of letrozole and CC offers a good second-line option for induction of ovulation in CCR-PCOS patients. However, the combination of CC and letrozole did not add any benefit over the use of letrozole alone regards ovulation rate, follicular volume, endometrial thickness, pregnancy rate and live birth rate.

A randomized, open phase IV exploratory clinical trial to evaluate the efficacy and safety of acupuncture on the outcome of induction of ovulation in women with poor ovarian response

Introduction:Women with infertility who have a poor ovarian responder (POR), characterized by a low number of retrieved oocytes after ovulation induction, often have a significantly reduced pregnancy rate after in vitro fertilization-embryo transfer (IVF-ET), due to the few transferred embryos. Acupuncture is a form of Korean Traditional Medicine. It involves the insertion of a microscopic needle at a specific point in the body, known as an acupuncture point or an acupoint. In this study, our purpose is to investigate how acupuncture affects the retrieval of mature oocytes after ovulation induction in patients with POR.Methods and analysis:This study will be a randomized clinical trial comprising an IVF-ET trial and an IVF-ET trial after acupuncture. Seventy patients will by enrolled and randomly assigned to either of the 2 groups. The study subjects will be required to be diagnosed as having POR. Participants will be divided into 2 groups: IVF-ET single treatment group, and acupuncture and IVF-ET combined treatment group. The study subjects will be required to participate in a 15-week trial involving 16 acupuncture treatments over a period of approximately 2 months before ovulation induction for oocyte retrieval. The primary assessment of all participants will be comparing the number of oocytes.Result:This treatment will be a therapeutic model for POR.Discussion:Our results will provide patients with POR as well as complementary and alternative medicine professionals, such as Korean medicine doctors, about the potential role of acupuncture in the treatment of POR. This will improve the quality of life in women with infertility and provide an important treatment option for patients with POR. Further studies can be performed to determine the optimal treatment for POR.

Letrozole versus clomiphene citrate in polycystic ovary syndrome: a meta-analysis of randomized controlled trials

Polycystic ovary syndrome (PCOS) is a common endocrine disturbance affecting women in the reproductive age group. The present study aimed to compare the effects of letrozole (LE) and clomiphene citrate (CC) for ovulation induction in women with PCOS. The PUBMED, Web of Science, and EMBASE databases were screened systematically for randomized controlled trials (RCTs) published from database inception to July 2017. Eleven RCTs involving 2255 patients were included, and data were independently extracted and analyzed using 95% risk ratios (RRs) and confidence intervals (CIs) based on a random- or fixed-effect model (as appropriate). Meta-analyses of nine RCTs comparing LE and CC ovulation induction, followed by timed intercourse, indicated that the former significantly increased the ovulation rate (RR=1.18; 95% CI 1.03-1.36, P=0.01), pregnancy rate (RR=1.34; 95% CI 1.09-1.64, P=0.006), and live birth rate (RR=1.55; 95% CI 1.28-1.88, P<0.00001). However, LE and CC did not differ significantly in terms of the multiple pregnancy and abortion rates. Furthermore, LE for ovulation induction significantly improved the pregnancy rate after IUI. LE is superior to CC for ovulation induction in patients with PCOS.

Effect of estradiol valerate on the pregnancy rate in patients receiving letrozole for induction of ovulation

Abstract Background Letrozole is as effective as clomiphene citrate for induction of ovulation in patients with PCOS. Adequate endometrial development is required for pregnancy to occur, and pregnancy rates were found to be higher when the endometrium reached at least 10 mm thickness. Objective To study the effect of estradiol valerate on the endometrial thickness and subsequently the pregnancy rate in PCOS cases receiving letrozole for induction of ovulation as compared to letrozole alone. Study design A randomized controlled study. Setting was at the infertility clinic of the Cytogenetic and Endoscopy Unit, Zagazig University Hospital. Material and methods The study included 273 patients who underwent ovulation induction and timed intercourse. Patients were divided into 2 groups: controlled ovarian stimulation was done in group 1 by letrozole with addition of estradiol valerate and in group 2 by letrozole alone. Results As regard the clinical pregnancy rate, we found a statistically significant difference between the 2 studied groups, with documented clinical pregnancy in 34 patients in group 1 compared to only 16 patients in group 2. Conclusion This study showed that the pregnancy rate achieved with letrozole/estradiol valerate combination was significantly higher than with letrozole alone. This was attributed to the improvement of endometrial thickness by estradiol valerate.

Comparison of pregnancy rates between patients with and without local endometrial scratching before intrauterine insemination

ObjectivesTo determine the implantation success of local endometrial injury in patients undergoing intrauterine insemination following ovulation induction with gonadotropins as an infertility treatment. Material and methodsIn this prospective randomized controlled trial, ovulation induction was performed with gonadotropins in 80 patients following intrauterine insemination. In 40 patients, local endometrial injury (scratch) was performed in the midluteal phase of the cycle preceding ovarian stimulation with a Novak curette to the posterior side of the endometrial cavity. ResultsFifteen pregnancies (37.5%) and 11 clinical pregnancies (27.5%) occurred in the intervention group, whereas eight pregnancies (20%) and five clinical pregnancies (12.5%) occurred in the control group. Although the pregnancy rates and clinical pregnancy rates were increased in the intervention group, no statistically significant difference was found between the intervention and control groups (pregnancy rates: P=0.084; clinical pregnancy rates: P=0.094). ConclusionPerforming local endometrial injury (scratch) in the cycle preceding ovulation induction in patients with a diagnosis of infertility and indication for intrauterine insemination increased the pregnancy and clinical pregnancy rates. This increase was not, however, statistically significant. More randomized, controlled, prospective studies with larger patient numbers are required before the use of iatrogenic induction of local endometrial injury can be recommended in routine clinical practice.

Efficacy of combined metformin- letrozole in comparison with metformin-laparoscopic ovarian diathermy in ovulation induction and reproductive outcome for women with clomiphene citrate resistant polycystic ovary syndrome

Background and objective: polycystic ovary syndrome(PCOS) is a common cause of infertility and is associated with chronic anovulation and hyperandrogenism.The aim of current study is to compare the effect of combined letrozole metformine to that of metformin-laparoscopic ovarian drilling (LOD) for ovulation induction in patients with PCOS.Materials and Methods: on the whole 138 ovarian cycles were studied in 60 patients with clomiphene citrate resistant PCOS in AL-Diwaniyah Maternity and Pediatrics Teaching Hospital during the period of June 2112-June 2114. All patients (n=60) received metformin 500mg /3times per day ,group A(n=30)received letrozole 5mg daily for 5 days repeated for 6 cycles, group B(n=30) underwent LOD and followed for six cycles. Outcome measures were ovulation rates, endometrialthickness, pregnancyrates, live birth rates and miscarriage rate.Results: ovulation rate was higher in group A than group B(63.33% versus 30.0%),a significant increase in endometrial thickness in group A than group B(9.9mm versus 9.03 mm).Live birth rate was higher in group A 83.33% compared to 33.33% in group B. There were no significant differences regarding miscarriage rates between both groups. No multiple pregnancy or ovarian hyper stimulation syndrome or congenital abnormality among live births were reported.Conclusions: Combinedletrozolemetformin seems to be a suitable second line ovulation inducing alternative to LOD in women with PCOS who do not respondwith clomiphene citrate.

Role of Letrozole Versus Clomiphene Citrate in Induction of Ovulation in Patients with Polycystic Ovarian Syndrome

Objective: the aim of this work is to compare the effect of Letrozole versus Clomiphene citrate (CC) in induction of ovulation in Polycyctic ovarian syndrome (PCOS) patients. Patients and methods: The study was conducted in Al Maadi Military Hospital at the department of Obstetrics and Gynecology (out-patient infertility clinic). The study is a prospective randomized study consisting of 100 Egyptian patients diagnosed as having PCOS. Patients were divided into two groups with randomization sheet and allocation concealment: Group (A): includes 50 females taking Letrozole 5mg tab orally once daily started in day 3 to day 7 of menstrual cycle for 3 cycles. Group (B): includes 50 females taking Clomiphene Citrate 100mg tab orally once daily started day 3 to day 7 of menstrual cycle for 3cycles. Trans-vaginal ultrasound was done from day 9-11 of the cycle to document ovulation rate, endometrial thickness and number of follicles and from day 14 (mid cycle day) to evaluate the target size of the follicle (18-22mm) and to assess the need to HCG administration. Results: Letrozole is significantly higher regarding endometrial thickness (Let 9.2mm Vs CC 8.0mm) and pregnancy rate (Let 48% Vs CC 28%), while Clomiphene Citrate (CC) is significantly higher regarding number of follicles (48%) as it produces multiple number of follicles compared to Letrozole (26%) which produces mono-follicle only. Both drugs are significantly similar regarding the ovulation rate. The study concluded that Letrozole can be used as first line therapy for induction of ovulation in polycystic ovary syndrome patients. Conclusion: The pharmacodynamics of Letrozole (does not deplete ERs, short half-life, keeps intact hypothalamic pituitary axis) ensures improved endometrial thickness and cervical mucus and monofollicular ovulation. Therefore, these factors may lead to a higher pregnancy rate and greater likelihood of singleton pregnancy.

Role of Letrozole Versus Clomiphene Citrate in Induction of Ovulation in Patients with Polycystic Ovarian Syndrome

Objective: the aim of this work is to compare the effect of Letrozole versus Clomiphene citrate (CC) in induction of ovulation in Polycyctic ovarian syndrome (PCOS) patients. Patients and methods: The study was conducted in Al Maadi Military Hospital at the department of Obstetrics and Gynecology (out-patient infertility clinic). The study is a prospective randomized study consisting of 100 Egyptian patients diagnosed as having PCOS. Patients were divided into two groups with randomization sheet and allocation concealment: Group (A): includes 50 females taking Letrozole 5mg tab orally once daily started in day 3 to day 7 of menstrual cycle for 3 cycles. Group (B): includes 50 females taking Clomiphene Citrate 100mg tab orally once daily started day 3 to day 7 of menstrual cycle for 3cycles. Trans-vaginal ultrasound was done from day 9-11 of the cycle to document ovulation rate, endometrial thickness and number of follicles and from day 14 (mid cycle day) to evaluate the target size of the follicle (18-22mm) and to assess the need to HCG administration. Results: Letrozole is significantly higher regarding endometrial thickness (Let 9.2mm Vs CC 8.0mm) and pregnancy rate (Let 48% Vs CC 28%), while Clomiphene Citrate (CC) is significantly higher regarding number of follicles (48%) as it produces multiple number of follicles compared to Letrozole (26%) which produces mono-follicle only. Both drugs are significantly similar regarding the ovulation rate. The study concluded that Letrozole can be used as first line therapy for induction of ovulation in polycystic ovary syndrome patients. Conclusion: The pharmacodynamics of Letrozole (does not deplete ERs, short half-life, keeps intact hypothalamic pituitary axis) ensures improved endometrial thickness and cervical mucus and monofollicular ovulation. Therefore, these factors may lead to a higher pregnancy rate and greater likelihood of singleton pregnancy.