The use of aromatase inhibitors in in vitro fertilization

Improved Pregnancy Outcomes and Endometrial Receptivity by Thawed Frozen Embryo Transfer in Mildly Stimulated Cycles with Letrozole Combined with Estrogen in Women with Unresponsive Thin Endometrium Compared to Standard Endometrial Preparation with Estrogen Alone: A Retrospective Study

Context

Infertile women undergoing frozen embryo transfer (FET) cycles may not show optimal endometrial growth with estrogens alone.

Aim

To evaluate clinical effect of mild stimulation with letrozole and estrogens on endometrial growth in comparison to standard endometrial preparation with oral and topical estrogens in infertile women with unresponsive thin endometrium undergoing FET.

Settings and design

Retrospective observational case-control study.

Material and methods

Forty women unresponsive to first AC-FET cycle were given mild stimulation with letrozole and estrogens as second LE-FET cycle for endometrial preparation (LE-FET study group) and compared with 40 historical controls who had received two cycles of AC-FET (AC-FET control group). Responses were assessed by optimal endometrial thickness (≥ 7 mm) and clinical pregnancy.

Statistical analysis

Descriptive statistics were elaborated by mean ± SD and percentages. Results were expressed by mean ± SD, unpaired t test for difference in endometrial thickness, chi square and Fisher exact test to compare the difference in pregnancy among both groups.

Results

Mean endometrial thickness was significantly increased in LE-FET study group (6.68 ± 2.09 mm) versus AC-FET control group (5.35 ± 1.90 mm). Higher clinical pregnancy rate was noted in study group as compared to control group (35% versus 12.5%).

Conclusion

This study suggests that letrozole with estradiol (LE-FET) compared to estradiol alone (AC-FET) for second cycle significantly increased endometrial thickness and improved clinical pregnancy rates in women with unresponsive thin endometrium after first AC-FET cycle with estradiol alone. Addition of letrozole to estrogen upfront for FET cycles may enhance endometrial receptivity and might improve pregnancy outcomes.

Pregnancy and neonatal outcomes of letrozole versus natural cycle frozen embryo transfer of autologous euploid blastocyst

PURPOSE

To investigate the pregnancy and neonatal outcomes of letrozole-stimulated frozen embryo transfer (LTZ-FET) cycles compared with natural FET cycles (NC-FET).

METHODS

Our retrospective cohort included all LTZ-FET (n = 161) and NC-FET (n = 575) cycles that transferred a single euploid autologous blastocyst from 2016 to 2020 at Stanford Fertility Center. The LTZ-FET protocol entailed 5 mg of daily letrozole for 5 days starting on cycle day 2 or 3. Outcomes were compared using absolute standardized differences (ASD), in which a larger ASD signifies a larger difference. Multivariable regression models adjusted for confounders: maternal age, BMI, nulliparity, embryo grade, race, infertility diagnosis, and endometrial thickness.

RESULTS

The demographic and clinical characteristics were overall similar. A greater proportion of the letrozole cohort was multiparous, transferred high-graded embryos, and had ovulatory dysfunction. The cohorts had similar pregnancy rates (67.1% LTZ vs 62.1% NC; aOR 1.31, P = 0.21) and live birth rates (60.9% LTZ vs 58.6% NC; aOR 1.17, P = 0.46). LTZ-FET neonates on average were born 5.7 days earlier (P < 0.001) and had higher prevalence of prematurity (18.6% vs. 8.0%NC, ASD = 0.32) and low birth weight (10.4% vs. 5.0%, ASD = 0.20). Both cohorts' median gestational ages (38 weeks and 1 day for LTZ; 39 weeks and 0 day for NC) were full term.

CONCLUSION

There were similar rates of pregnancy and live birth between LTZ-FET and NC-FET cycles. However, there was a higher prevalence of prematurity and low birth weight among LTZ-FET neonates. Reassuringly, the median gestational age in both cohorts was full term, and while the difference in gestational length of almost 6 days does not appear to be clinically significant, this warrants larger studies.

Letrozole cotreatment improves the follicular output rate in high-body-mass-index women with polycystic ovary syndrome undergoing IVF treatment

BACKGROUND

Women who have polycystic ovary syndrome (PCOS) with high body mass index (BMI) typically have an attenuated ovarian response and decreased follicular size, which are linked to unfavourable clinical outcomes following in vitro fertilization (IVF) therapy. The follicular output rate (FORT), a qualitative indicator of follicular response, seems to be positively linked to the clinical outcomes of IVF. Progestin-primed ovarian stimulation (PPOS) has become an alternative to gonadotropin-releasing hormone (GnRH) analogues to inhibit the premature luteinizing hormone (LH) surge. As letrozole (LE) shows promise in enhancing ovarian response, we compared PPOS with and without LE for PCOS in high BMI women with a focus on the FORT and associated clinical and pregnancy outcomes.

METHODS

For the recruited 1508 women, ten variables including AFC; age; basal sex hormone level; BMI; infertility type; period of infertility and number of previous IVF attempts were chosen in the propensity score matching (PSM) model to match 1374 women who taken the MPA+ hMG protocol with 134 women who received the MPA+ hMG+ LE treatment at a 1:1 ratio. FORT was selected as the primary outcome measure. The number of oocytes retrieved, viable embryos, hMG dosage, duration, oocyte maturity rate, fertilization rate, and implantation rate were established as secondary outcomes.

RESULTS

FORT was substantially elevated in the MPA+hMG+LE group compared with the MPA+hMG group (61% [35%, 86%] vs. 40% [25%, 60%], P <.001). Interestingly, the LE cotreatment group had a considerably lower mature oocyte rate despite having a similar number of mature oocytes and embryos recovered. The average hMG dosages and durations in the study group were similar to those in the control group. The implantation rate in the study group was numerically higher but without statistic significant than that in the control groups (43.15% (107/248) vs. 38.59% (115/298), OR 1.008, 95% CI 0.901-1.127; P >.05).

CONCLUSION

The effect of LE combined with PPOS on FORT is better than the effect of the standard PPOS treatment in women with PCOS and a high BMI, but there is no substantially beneficial impact on pregnancy outcomes or the cycle features of COS, including consumption of hMG.

Letrozole cotreatment with progestin-primed ovarian stimulation in women with polycystic ovary syndrome undergoing IVF treatment

Background: Progestin is an alternative to gonadotropin-releasing hormone (GnRH) analogues in the follicular phase to suppress the premature luteinizing hormone (LH) surge in women with polycystic ovary syndrome (PCOS). However, progestin-primed ovarian stimulation (PPOS) is always accompanied by increased pituitary suppression and gonadotropin consumption. Previous studies suggested that letrozole appeared to have the potential to reduce the total gonadotropin dose required for ovarian stimulation. A retrospective cohort study was performed to evaluate the efficacy of PPOS with or without letrozole in infertile women with PCOS.

Methods: This retrospective cohort study included 448 women with PCOS who underwent controlled ovarian stimulation (COS) with human menopausal gonadotropin (hMG) and medroxyprogesterone acetate (MPA) (n = 224) or hMG and MPA cotreatment with LE (n = 224) from January 2018 to March 2021 after propensity-score matching. The primary outcome measure was the hMG dose. The secondary outcomes were the durations of ovarian stimulation, the implantation rate, the number of oocytes retrieved and viable embryos, oocyte maturity and fertilization rates, the percentage of women with profound pituitary suppression (luteinizing hormone [LH] <1.0 IU/L on the trigger day).

Results: The hMG doses (1949.89 ± 725.03 IU vs 2017.41 ± 653.32 IU,p > 0.05) and durations of ovarian stimulation (9.03 ± 1.79 days vs 9.21 ± 2.18 days,p > 0.05) were similar between the two groups. The implantation rate was significantly higher in the study group (MPA + hMG + LE) than in the control group (MPA + hMG) (42.22 vs 34.69%, p < 0.05). The numbers of oocytes and embryos retrieved were similar between the two groups. Interestingly, letrozole cotreatment was associated with decreased oocyte maturity and fertilization rates in comparison with standard PPOS protocols even though mature and fertilized oocyte yields were comparable. Compared with those in the control group, the LH values on the trigger day were significantly higher in the study group, together with significantly reduced pituitary suppression.

Conclusion: Letrozole combined with PPOS cannot reduce hMG consumption in PCOS patients undergoing IVF treatment and shows no beneficial effect on cycle characteristics of COS. However, letrozole supplementation manifests as a superior implantation rate to that of the standard PPOS protocol in women with PCOS.

Systematic review update and meta-analysis of randomized and non-randomized controlled trials of ovarian stimulation versus artificial cycle for endometrial preparation prior to frozen embryo transfer in women with polycystic ovary syndrome

PURPOSE

This systematic review and meta-analysis aimed to compare the short-term reproductive and long-term obstetric outcomes after endometrial preparations by ovarian stimulation protocols and hormone replacement therapy (HRT) in women with polycystic ovary syndrome (PCOS) prior to frozen embryo transfer (FET).

METHOD

PubMed, EMBASE, Web of Science and the Cochrane Library were searched to identify relevant studies. Primary outcome was live birth rate, secondary outcomes included the rates of clinical pregnancy, miscarriage, implantation and hCG-postive, cycle cancellation, ectopic pregnancy, preterm birth, preeclampsia, gestational hypertension, gestational diabetes mellitus and abnormal placentation.

RESULTS

Nine studies, including 8327 patients with PCOS, were identified. Live birth rate was significantly higher (RR = 1.11, 95% CI = 1.03-1.19) and miscarriage rate (RR = 0.60, 95% CI = 0.46-0.78) was significantly lower in stimulated protocol compared to the rates in HRT. While the rates of ongoing pregnancy, clinical pregnancy, implantation, hCG-positive, cycle cancellation and ectopic pregnancy showed no significant difference between the two protocols. Compared HRT with different stimulation protocols, significantly higher clinical pregnancy rate (RR = 1.54, 95% CI = 1.20-1.98) were found in letrozole group, but not in the other subgroups. For the obstetric outcomes, the preterm birth and preeclampsia rates were significantly lower in the stimulated group compared to that in the HRT group (RR = 0.85, 95% CI = 0.74-0.98; RR = 0.57, 95% CI = 0.40-0.82, respectively), while gestational hypertension, gestational diabetes mellitus and abnormal placentation rates showed no significant difference.

CONCLUSIONS

The present data suggest that ovarian stimulation protocol as an endometrial preparation regimen prior to FET might be superior to HRT protocol with a significantly higher rate of live birth, lower risk of miscarriage, preterm birth and preeclampsia. Our study showed stimulated protocol is better than HRT regimen as an endometrial preparation for women with PCOS. However, quality of the evidence is low, more well-designed RCT studies are still needed to confirm the results before clinical recommendation, particularly direct comparisons between letrozole and other stimulated regimens.

Ovulation induction regimens are associated with a higher rate of livebirth after frozen single-blastocyst transfer among women with polycystic ovary syndrome

BACKGROUND

Hormone replacement therapy (HRT) regimen was suggested to be associated with a decreased rate of livebirth and a higher risk of hypertensive disorders of pregnancy (HDP) after frozen cleavage stage embryo transfer in women with polycystic ovary syndrome (PCOS). With the dramatically increased use of elective single embryo transfer, there is great need to explore the impacts of different endometrial preparation regimens on frozen single-blastocyst transfer in women with PCOS.

METHODS

In this study, a total of 3941 women who diagnosed with PCOS and underwent single-blastocyst transfer during their first cycles of frozen embryo transfer (FET) between March 2012 and December 2020 were included. We retrospectively compared the pregnancy and neonatal outcomes after frozen single-blastocyst transfer with endometrial preparation by HRT regimen (n = 3540), ovulation induction by human menopausal gonadotropin (hMG) regimen (n = 226), and ovulation induction by letrozole regimen (n = 175).

RESULTS

After adjustment for confounders with multivariable logistic regression, the hMG regimen group [(58.4% vs. 49.6%; adjusted odds ratio (aOR): 1.43; 95% confidence interval (CI): 1.09-1.89)] and letrozole regimen group (58.9% vs. 49.6%; aOR: 1.42; 95% CI: 1.04-1.93) were associated with a higher rate of livebirth (primary outcome), compared with the group with HRT regimen. As to the secondary outcomes, the rate of pregnancy loss in the hMG regimen group (22.8% vs. 30.3%; aOR: 0.69; 95% CI: 0.48-1.00) and letrozole regimen group (16.9% vs. 30.3%; aOR: 0.48; 95% CI: 0.30-0.78) was also lower than that in the HRT regimen group. The pregnancy outcomes between the hMG regimen group and the letrozole regimen group were similar. We did not observe significant difference in the incidences of maternal and neonatal complications among these three groups.

CONCLUSION

Ovulation induction regimen with letrozole or hMG for endometrial preparation was associated with a higher livebirth rate and a lower pregnancy loss rate in frozen single-blastocyst transfer cycles among women with PCOS.

Comparison of Perinatal Outcomes of Letrozole-Induced Ovulation and Hormone Replacement Therapy Protocols in Patients With Abnormal Ovulation Undergoing Frozen-Thawed Embryo Transfer: A Propensity Score Matching Analysis

BACKGROUND

With the increasing use of frozen embryo transfer (FET), the best endometrial preparation protocol is continuously being discussed. The hormone replacement therapy (HRT) cycle and letrozole-induced ovulation (L-OI) cycle are available protocols for patients with abnormal ovulation. Previous comparisons of the two protocols have focused on pregnancy outcomes, with less attention to perinatal outcomes, and population heterogeneity was large; thus, convincing conclusions about which protocol is more appropriate could not be drawn.

METHODS

We performed a retrospective cohort study using propensity score matching (PSM) analysis for a population of patients undergoing FET cycles in the reproductive center of the Third Affiliated Hospital of Zhengzhou University from January 2016 to September 2020. The main outcome measures were clinical pregnancy rate, live birth rate, very preterm delivery (VPTD), preterm delivery (PTD), low birth weight (LBW), macrosomia, small for gestational age (SGA), large for gestational age (LGA), hypertensive disorders of pregnancy (HDP), gestational diabetes mellitus (GDM), premature rupture of membranes (PROM), placenta previa, and congenital abnormality.

RESULTS

A total of 8010 women were enrolled. Due to the large heterogeneity among the patients, we conducted 1:1 PSM, and 1461 women matched in each group. Compared with the HRT group, the L-OI group had a smaller proportion of thin endometrium (27.38% vs. 41.07%) and thicker endometrium on the day of embryo transfer (9.63 ± 1.82 vs. 8.91 ± 1.38). There were no significant differences in clinical pregnancy rate, early abortion rate or live birth rate between the groups. There was no significant difference in perinatal outcomes of singleton live birth, including VPTD, PTD, postterm delivery, LBW, macrosomia, SGA, LGA, GDM, HDP, placenta previa, and congenital malformation.

CONCLUSION

For women with abnormal ovulation, the pregnancy and perinatal outcomes of HRT and L-OI protocols are reassuring. It seems that both protocols are safe and effective for endometrial preparation in frozen-thawed embryo transfer in the clinic.

The Effect of Spontaneous LH Surges on Pregnancy Outcomes in Patients Undergoing Letrozole-HMG IUI: A Retrospective Analysis of 6,285 Cycles

BACKGROUND

To date, no consensus has been reached on whether to wait for spontaneous luteinizing hormone (LH) surge to occur or to trigger ovulation regardless of the presence of an LH surge for achieving higher success rate in intrauterine insemination (IUI) cycles. Therefore, we hope to investigate the effect of the presence of a spontaneous LH surge on pregnancy outcomes in letrozole-human menopausal gonadotropin (LE-HMG) IUI cycles.

METHODS

In this retrospective cohort study, a total of 6,285 LE-HMG IUI cycles were included between January 2010 and May 2021. Cycles were categorized into three groups: the trigger + LH surge group, the trigger only group, and the LH surge only group. The primary outcome measure was the clinical pregnancy rate. A logistic regression analysis was performed to explore other risk factors affecting the clinical pregnancy rate.

RESULTS

No significant differences were observed in biochemical pregnancy rate (P =0.640), clinical pregnancy rate (P =0.702), ongoing pregnancy rate (P =0.842), and live birth rate (P =0.951) among the three groups. The binary logistic regression analysis also confirmed that the existence of an LH surge was not associated with clinical pregnancy. There was a difference in ectopic pregnancy rates (P =0.045), but logistic regression showed that the presence of a spontaneous LH surge has no association with ectopic pregnancy. Nonetheless, patients with lead follicles within 18.1-20.0 mm/20.1-22.0 mm and a long duration of LE treatment were less likely to get ectopic pregnant compared with patients with 14.1-16.0 mm lead follicles and shorter LE treatment (OR: 0.142, 95% CI: 0.023-0.891, P =0.037; OR: 0.142, 95% CI: 0.022-0.903, P =0.039; OR: 0.445, 95% CI: 0.235-0.840, P = 0.013).

CONCLUSIONS

The presence of a spontaneous LH surge in triggered LE-HMG IUI cycles does not appear to improve pregnancy rates. Thus, we suggest that waiting for an LH surge to occur is not necessary in triggered LE-HMG IUI cycles.

Clinical pregnancy rates among anovulatory and oligoovulatory women after letrozole versus hormone replacement therapy in frozen-thawed embryo transfer cycles

This cohort study investigated whether letrozole versus hormone replacement therapy (HRT) results in higher live birth rate among anovulatory and oligoovulatory women in frozen-thawed embryo transfer (FET) cycles. It was conducted from 1st February 2018 to 31st January 2019 and included 261 anovulatory and oligoovulatory women. Since letrozole has become an effective alternative to HRT cycles, 121 patients received letrozole in 121 cycles from 1st February 2018 to 31st January 2019 and were compared to 140 HRT FET cycles among 140 women from 1st February 2017 to 31st January 2018. The primary outcome was live birth rate. Secondary outcomes were clinical pregnancy, multiple pregnancy and miscarriage rates. Clinical pregnancy and live birth rates of transferred cleavage embryos were higher in the letrozole compared to the HRT group (36/65 (55.3%) vs. 20/110 (18.1%), p < 0.001) and (25/65 (38.4%) vs. 17/110 (15.4%), p < 0.001) respectively, whilst these rates were similar for transferred blastocyst embryos. Miscarriage and multiple pregnancy rates were similar between groups. The letrozole group was older than the HRT group (31.8 ± 5.1 vs. 29.9 ± 5.1 years, p = 0.002) and more smoked cigarettes (p = 0.035). Groups were similar regarding BMI, male versus non-male indication for fertility treatment, peak oestradiol levels, and numbers of oocytes retrieved, blastocysts, frozen and transferred embryos. Letrozole compared to HRT might improve live birth and clinical pregnancy rates among anovulatory and oligoovulatory women undergoing FET cycles.

Frozen Embryo Transfer in Mildly Stimulated Cycle With Letrozole Compared to Natural Cycle in Ovulatory Women: A Large Retrospective Study

OBJECTIVE

To evaluate the clinical effect of mild stimulation with letrozole on pregnancy outcomes in ovulatory women undergoing frozen embryo transfer (FET) compared to natural cycle.

DESIGN

Retrospective observational study.

SETTING

Tertiary care academic medical center.

POPULATION

A total of 6,874 infertile women with regular menstrual cycles (21-35 days) met the criteria for this study in the period from 2013 to 2020.

METHODS

All patients who were prepared for and underwent FET were divided into two groups: a modified natural cycle (NC) group (n=3,958) and a letrozole cycle group (n=2,916).

MAIN OUTCOME MEASURES

The primary outcome of the study was clinical pregnancy rate. Secondary outcome measures were endometrial thickness, rates of implantation, positive HCG test, live birth, early miscarriage and ectopic pregnancy.

RESULTS

The clinical pregnancy rate was not statistically different between the modified NC-FET group and the letrozole-FFT group before (crude OR 0.99, 95% CI 0.90-1.09, P=0.902>0.05) and after propensity score matching (PSM) (crude OR 1.01, 95% CI 0.91-1.12, P=0.870>0.05). After multivariable logistic regression analysis, the clinical pregnancy rate remained insignificant before (adjusted OR 1.00, 95% CI 0.91-1.10, P=0.979>0.05) and after matching (adjusted OR 1.00, 95% CI 0.89-1.11, P=0.936>0.05), respectively. Similarly, in the crude and adjusted analysis, the positive HCG test, implantation, live birth and early miscarriage rates were also comparable in the letrozole-FFT group and modified NC-FET group before and after matching. Furthermore, the endometrial thickness of letrozole-FFT group was similar to that of modified NC-FET group with adjusted analysis.

CONCLUSION

Our observation suggests that mild stimulation with letrozole could produce similar pregnancy outcomes in ovulatory patients who undergo FET when compared with a natural cycle.

Comparison of Pregnancy and Neonatal Outcomes of Single Frozen Blastocyst Transfer Between Letrozole-Induction and HRT Cycles in Patients With Abnormal Ovulation

BACKGROUND

The use of frozen embryo transfer (FET) cycles has dramatically risen. The optimal endometrial preparation method for women undergoing FET is of utmost importance to provide the optimal chances of pregnancy. For patients with abnormal ovulation in particular, there have been few studies on FET protocols; notably, most of these studies focus only on the clinical pregnancy rate or live birth rate (LBR) and pay little attention to the regimen's safety for offspring.

METHODS

It was a retrospective cohort study. First FET cycle with a single blastocyst from whole embryo frozen IVF/ICSI at the Reproductive Center of Third Affiliated Hospital of Zhengzhou University between January 2016 and January 2020. The LBR was the primary outcome of interest. The secondary outcome measures were miscarriage rate and offspring safety, including preterm birth, low birthweight (LBW), small-for-gestational age (SGA), macrosomia and large-for-gestational age (LGA).

RESULTS

In total, 2782 FET cycles met the eligibility criteria for analysis. Additionally, there were 1178 singleton births from FET cycles. The clinical pregnancy rate was 58.4% in the L-FET group and 54.5% in the HRT group, with no statistical significance (P=.116). The miscarriage rate was higher in the HRT group than in the L-FET group (21.7% vs. 14.3%, P=.005). The LBR was significantly higher in the L-FET group than in the HRT group (49.6% vs. 41.7%, P=.001). Neonatal outcomes were similar between the two groups. After adjustments for confounding factors, the LBR was higher in the L-FET group (aOR 1.30, 95% CI 1.06-1.58). The rate of miscarriage was lower in the L-FET group (aOR 0.63, 95% CI 0.44-0.90).

CONCLUSION

For patients with abnormal ovulation, the L-FET regimen has a higher LBR and lower miscarriage rate than HRT. The neonatal outcomes were similar between the two groups.

The effect of letrozole versus artificial hormonal endometrial preparation on pregnancy outcome after frozen-thawed embryos transfer cycles: a randomized clinical trial

BACKGROUND

Considering that clinical trial studies are limited in polycystic ovary syndrome (PCOS) patients, and there is no consensus on an optimum endometrial preparation protocol for frozen embryo transfer (FET), the present study was designed as a randomized clinical trial to compare the reproductive outcomes following stimulated cycles with letrozole plus human menopausal gonadotropin (HMG) for endometrial preparation compared with routine AC-FET.

METHODS

This randomized controlled trial was carried out on infertile PCOS patients who underwent IVF/ICSI and FET cycles in Arash Women's Hospital affiliated to Tehran University of Medical Sciences between September 2018 and January 2020. PCOS diagnosis was based on the Rotterdam criteria. Eligible patients were randomly allocated into two groups: stimulated cycle with letrozole plus (HMG) (intervention group) and routine artificial hormonal endometrial preparation (control group).

RESULTS

One hundred seventy-seven infertile patients were recruited for participation in the study. Of these, 57 women were excluded due to non-eligibility for entering the study, and a total of 120 patients were randomly assigned to two study groups. After follow up, the cycle outcomes of 57 patients in the intervention group and 59 patients in the control group were compared. The data analysis showed that the two groups did not have significant differences in fundamental and demographic characteristics. After the intervention, there were no significant differences in implantation rate, chemical, ectopic, and clinical pregnancy rates between groups. Moreover, the rates of miscarriage and ongoing pregnancy were similar between groups (P > 0.05).

CONCLUSIONS

We found similar pregnancy outcomes with two endometrial preparation methods. Noting that each treatment centre should select the most beneficial and cost-effective method with the least adverse effects for patients, letrozole preparations for FET could be incorporated into possible options; however, establishing this approach as first-line treatment is premature in light of current evidence, and future randomized clinical trials with larger sample sizes are required for widespread application.

TRIAL REGISTRATION

The study was also registered in the Iranian Registry of Clinical Trials on March 20th, 2020. ( IRCT20090526001952N12 at www.irct.ir , registered retrospectively).

Letrozole use during frozen embryo transfer cycles in women with polycystic ovary syndrome

OBJECTIVE

To investigate whether live birth rate (LBR) following frozen-thawed embryo transfer in letrozole-stimulated cycles (L-FET) differs from LBR after artificial-cycle frozen-thawed embryos transfers (AC-FET) in women with polycystic ovary syndrome (PCOS).

DESIGN

Retrospective cohort study.

SETTING

Tertiary-care academic medical center.

PATIENT(S)

A total of 2,664 patients with PCOS who fulfilled the inclusion criteria were enrolled in the period from 2011 to 2016.

INTERVENTIONS(S)

Letrozole use versus hormone replacement therapies during FET.

MAIN OUTCOME MEASURE(S)

LBR per embryo transfer was the primary outcome. The secondary end points included ongoing and clinical pregnancy rate, cancellation rate, endometrial thickness, and pregnancy loss rate. Multivariable logistic regression analysis was performed to adjust for potential confounders.

RESULT(S)

In our crude analysis, LBR per embryo transfer was similar between groups (54.4% in the L-FET vs. 50.7% for the AC-FET). The crude odds of pregnancy loss was significantly lower in L-FET compared with AC-FET (9.1% vs. 17%). Nonetheless, after adjusting for possible confounding factors, LBR was significantly higher in L-FET compared with AC-FET. Moreover, the rates of pregnancy loss remained consistently lower in the L-FET group than in the AC-FET group.

CONCLUSION(S)

In patients with PCOS undergoing FET, letrozole use for endometrial preparation was associated with higher LBR compared with artificial cycles, albeit after statistical adjustment for confounding factors. Future prospective randomized studies are needed to verify our findings.

Effect of letrozole added to gonadotropins in controlled ovarian stimulation protocols on the yield and maturity of retrieved oocytes

We aimed to evaluate the effect of co-administration of letrozole and gonadotropins during ovarian stimulation on oocyte yield and maturation in breast cancer patients prior to chemotherapy. A retrospective cohort design was used comparing oocyte cryopreservation cycles among patients with breast cancer patients with other oncological indications and women undergoing elective oocyte cryopreservation. All patients were treated with GnRH antagonist protocol using GnRH agonist for final oocyte maturation. The breast cancer group was additionally treated with letrozole (5 mg/d) from the first day of treatment until the day of oocyte retrieval. The cohort included 418 patients: 145 breast cancer patients, 168 with other oncological indications, and 105 patients who chose to undergo elective oocyte cryopreservation. There were no significant differences among the groups in the number of retrieved oocytes or proportion of mature oocytes. On multivariate linear regression models, co-treatment with letrozole was not a significant factor for the number of retrieved oocytes or for oocyte maturation rate after controlling for age, body mass index (BMI), and FSH dose. We conclude that the addition of letrozole to gonadotropins does not increase the number of oocytes retrieved or the oocyte maturation rate.

Pregnancy and neonatal outcomes following letrozole use in frozen-thawed single embryo transfer cycles

STUDY QUESTION

Are pregnancy and neonatal outcomes following letrozole use comparable with natural and HRT cycles in patients undergoing single frozen-thawed embryo transfer (FET)?

SUMMARY ANSWER

Letrozole use was significantly associated with higher rates of clinical pregnancy, clinical pregnancy with fetal heart beat and live birth, and with a lower rate of miscarriage, compared with natural and HRT cycles.

WHAT IS KNOWN ALREADY

Letrozole is the most commonly used aromatase inhibitor for mild ovarian stimulation in ART. However, the effect of letrozole on pregnancy and neonatal outcomes in FET are not well known.

STUDY DESIGN SIZE, DURATION

A retrospective cohort study was conducted using data from the Japanese national ART registry between 2012 and 2013.

PARTICIPANTS/MATERIALS SETTING METHODS

A total of 110 722 single FET cycles with letrozole (n = 2409), natural (n = 41 470) or HRT cycles (n = 66 843) were included. The main outcomes were the rates of clinical pregnancy, clinical pregnancy with fetal heart beat, miscarriage and live birth. Adjusted odds ratios and relative risks (RRs) were calculated using a generalized estimating equation adjusting for correlations within clinics.

MAIN RESULTS AND THE ROLE OF CHANCE

The rates of clinical pregnancy, clinical pregnancy with fetal heart beat, and live birth were significantly higher, while the rate of miscarriage was significantly lower in the letrozole group compared with the natural and HRT groups. In blastocyst stage transfers, the adjusted RRs for clinical pregnancy with fetal heart beat of letrozole compared with natural and HRT cycles were 1.48 (95% CI: 1.41-1.55) and 1.62 (95% CI: 1.54-1.70), respectively. Similarly, the adjusted RRs of letrozole for miscarriage compared with natural and HRT cycles were 0.91 (95% CI: 0.88-0.93) and 0.84 (95% CI: 0.82-0.87), respectively. Neonatal outcomes were mostly similar in letrozole, natural and HRT cycles.

LIMITATIONS REASONS FOR CAUTION

Important limitations of this study included the lack of information concerning the reasons for selecting the specific FET method, parity, the number of previous ART failures, embryo quality and the dose and duration of letrozole intake.

WIDER IMPLICATIONS OF THE FINDINGS

These results suggest that letrozole use may improve clinical pregnancy, clinical pregnancy with fetal heart beat, and live births and reduce the risk of miscarriage in patients undergoing single FET cycles.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was used for this study. There are no conflicts of interest.

TRIAL REGISTRATION NUMBER

Not applicable.

No increased risk of major congenital anomalies or adverse pregnancy or neonatal outcomes following letrozole use in assisted reproductive technology

STUDY QUESTION

Does letrozole use increase the risk of major congenital anomalies and adverse pregnancy and neonatal outcomes in fresh, single-embryo transfer?

SUMMARY ANSWER

Letrozole significantly decreases the risk of miscarriage and does not increase the risk of major congenital anomalies or adverse pregnancy or neonatal outcomes compared with natural cycles in patients undergoing ART.

WHAT IS KNOWN ALREADY

Letrozole is the most commonly used aromatase inhibitor for mild ovarian stimulation in ART. However, its safety in terms of pregnancy and neonatal outcomes is unclear.

STUDY DESIGN SIZE, DURATION

This retrospective cohort study used data from the Japanese national ART registry from 2011 to 2013.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 3136 natural cycles and 792 letrozole-induced cycles associated with fresh, single-embryo transfer and resulting in a clinical pregnancy were included in the analysis. The main pregnancy outcomes were miscarriage, ectopic pregnancy and still birth, and the neonatal outcomes were preterm delivery, low birth weight, small/large for gestational age and major congenital anomalies. Terminated pregnancies were included in the analysis of major congenital anomalies. Odds ratios (ORs) and 95% CIs were calculated using multivariate logistic regression analysis adjusted for maternal age and calendar year.

MAIN RESULTS AND THE ROLE OF CHANCE

The risk of miscarriage was significantly lower in women administered letrozole (adjusted OR [aOR], 0.37, 95% CI, 0.30-0.47, P < 0.001). There was no significant difference in the overall risk of major congenital anomalies between the two groups (natural cycle 1.5% vs letrozole 1.9%, aOR, 1.24, 95% CI, 0.64-2.40, P = 0.52), and no increased risk for any specific organ system. Subgroup analysis demonstrated that the risk of major congenital anomalies was not increased in patients who underwent either in vitro fertilization or ICSI, or in those who received early cleavage stage or blastocyst embryo transfer. All other pregnancy and neonatal outcomes were comparable between the two groups.

LIMITATIONS REASONS FOR CAUTION

Despite the large sample size, we were only able to rule out the possibility that letrozole might cause large increases in birth-defect risks in ART patients.

WIDER IMPLICATIONS OF THE FINDINGS

The results suggest that letrozole stimulation reduces the risk of miscarriage, with no increase in the risk of major congenital anomalies or adverse pregnancy or neonatal outcomes compared with natural cycles in women undergoing ART. Letrozole may thus be a safe option for mild ovarian stimulation.

STUDY FUNDING/COMPETING INTERESTS

None.

TRIAL REGISTRATION NUMBER

Not applicable.

Comparison of The Effectiveness of Clomiphene Citrate versus Letrozole in Mild IVF in Poor Prognosis Subfertile Women with Failed IVF Cycles

BACKGROUND

Our objective was to evaluate the effectiveness of clomiphene citrate (CC) vs. letrozole (L) plus human menopausal gonadotropin (hMG) in gonadotropin releasing hormone (GnRH) antagonist protocol in poor prognosis women with previous failed ovarian stimulation undergoing intracytoplasmic sperm injection (ICSI).

MATERIALS AND METHODS

This retrospective cohort study included cycles with CC and L plus hMG/GnRH antagonist protocols of 32 poor responders who had failed to have ideal follicles to be retrieved during oocyte pick-up (OPU) or embryo transfer (ET) at least for 2 previous in vitro fertilization (IVF) cycles with microdose flare protocol or GnRH antagonist protocol from January 2006 to December 2009. Main outcome measures were implantation, clinical pregnancy and live birth rates per cycle. Duration of stimulation, mean gonadotropin dose used, endometrial thickness, number of mature follicles, serum estradiol (E2) and progesterone (P) levels on the day of human chorionic gonadotropin (hCG) administration, number of retrieved oocytes and fertilization rates were also evaluated.

RESULTS

A total number of 42 cycles of 32 severe poor responders were evaluated. Total gonadotropin consumption was significantly lower (1491 ± 873 vs. 2808 ± 1581 IU, P=0.005) and mean E2 level on the day of hCG injection were significantly higher in CC group than L group (443.3 ± 255.2 vs. 255.4 ± 285.2 pg/mL, P=0.03). ET, overall pregnancy and live birth rates per cycle were significantly higher in CC than L protocol (27.2 vs. 15%, 13.6 vs. 0% and 4.5 vs. 0%, respectively, P<0.05).

CONCLUSION

Severe poor responders who had previously failed to respond to microdose or GnRH antagonist protocols may benefit from CC plus hMG/GnRH antagonist protocol despite high cancellation rate.

Clinical use of fertility agents and risk of breast cancer: a recent update for an old problem

PURPOSE OF REVIEW

Female infertility is today a very common, expanding problem and therefore restoring fertility strategies are increasing in the last few years. An association between ovarian stimulation and breast cancer risk has been hypothesized, but the question has not yet been clarified.

RECENT FINDINGS

In the last 2 years, many important studies have been published on this topic. A lot of new combinations of drugs are in experimentation and other recent drugs are already in current use, such as aromatase inhibitors. Furthermore, the data from older studies were investigated by two recent meta-analyses.

SUMMARY

Infertility affects many couples in western countries and the use of fertility stimulation techniques is widespread in the last few years, determining personal anxiety, social costs, and organizing difficulties. It is well known that one of the most important causative agents for the development of breast cancer is the proliferative activity of endogenous and exogenous female hormones. Therefore, it seems appropriate to investigate the risk of breast cancer derived from the use of hormonal therapies in infertile women. The final clarification of this question is very important so that all women can realize their dream of having children, with the certainty of not being exposed to an increased risk of breast cancer.

Clinical review: The use of aromatase inhibitors for ovulation induction and superovulation

CONTEXT

Anovulation is likely responsible for 20% of female infertility. Although clomiphene citrate remains the first-line therapy for ovulation induction in anovulatory patients who are not estrogen-deficient and to treat unexplained infertility, there remains a discrepancy between ovulation and conception rates with its use, attributed to its antiestrogenic effects on cervical mucus and the endometrium. Alternative agents, including aromatase inhibitors, have been used that have not been associated with these side effects.

EVIDENCE ACQUISITION

A literature search was conducted to specifically explore the use of aromatase inhibitors for ovulation induction and superovulation.

EVIDENCE SYNTHESIS

Recent studies have found that aromatase inhibitors may be safe and useful agents for ovulation induction in patients with polycystic ovarian syndrome as well a treatment option for superovulation in patients with either unexplained infertility or endometriosis.

CONCLUSIONS

Aromatase inhibitors may be an effective alternative treatment to clomiphene citrate for both ovulation induction and superovulation.