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.

PP104. Pregnancy-induced hypertension is a strong risk factor for hypertension just 5 years after delivery: A double cohort study at the National Center for Child Health and Development and Showa University Hospital, Tokyo.

INTRODUCTION: Pregnancy-induced hypertension (PIH) is associated with increased risk for cardiovascular diseases later in life. OBJECTIVES: To assess the prevalence of subsequent hypertension and other life-style diseases five years after delivery in women who experienced pregnancy- induced hypertension. METHODS: A total of 1527 women who delivered singletons were registered at the National Center for Child Health and Development and Showa University Hospital Mother and child health center of integrated perinatal period between 2003 and 2005. After five years, these women were invited to participate in this study by mail, and 816 women completed the analysis. The women visited our hospital and underwent a medical examination. Women who were pregnant and nursing at the time when the physical examination was conducted were excluded from this survey. The outcomes assessed included the prevalences of hypertension, diabetes, and dyslipidemia. RESULTS: The number of PIH cases was 27 (3.3%: PIH group), whereas 787 women were used as controls subjects. The mean blood pressure five years after delivery was higher in the PIH group than in the control group (91.6±15.5mmHg vs 82.4±8.8mmHg, respectively; p<0.001), and the prevalence of hypertension five years after labor was 18.5% in the PIH group and 2.9% in the controls (odds ratio UOR Y=6.2; 95% confidence interval (CI)=2.2-17.5; p=0.003). Moreover, regarding high-normal blood pressure (>130/85mmHg), the prevalence was 33.4% in the PIH group and 6.1% in the control subjects (OR=7.2; 95% CI=3.1-16.3; p=0.003). No differences in the prevalences of subsequent diabetes or dyslipidemia were observed. CONCLUSION: Five years after the index pregnancy, women who experienced PIH exhibit an increased risk for subsequent hypertension. Therefore, the blood pressure of women with history of PIH should be regularly monitored after delivery.