Low-dose clomiphene citrate does not reduce implantation and live birth rates in otherwise unstimulated modified natural cycle IVF-retrospective cohort study.

RESEARCH QUESTION: Does antioestrogen effect of clomiphene citrate (CC) on the endometrium reduce implantation and thereby decrease pregnancy and live birth rate per transferred embryo? METHODS: In this cohort, unstimulated IVF cycles modified with clomiphene citrate (CC-NC-IVF) and unstimulated, natural IVF cycles (NC-IVF) conducted between 2011 and 2016 were included. CC was applied in a dosage of 25mcg per day, starting on cycle day 7 until ovulation trigger day. Primary outcomes were clinical pregnancy rate, defined as amniotic sac visible in ultrasound, and live birth rate per transferred embryo. Miscarriage rate calculated as amniotic sac not ending in a live birth was secondary outcome. A modified mixed-effect Poisson regression model was applied, and adjustments were made for female age, parity, type and cause of infertility. Additionally, stratification by parity and age was performed. RESULTS: Four hundred and ninety-nine couples underwent a total of 1042 IVF cycles, 453 being NC-IVF and 589 being CC-NC-IVF cycles. Baseline characteristics of both groups did not differ. Addition of CC did neither decrease clinical pregnancy rate (aRR 0.86; 95% CI 0.67-1.12) nor live birth rate per transferred embryo (aRR 0.84; 95% CI 0.62-1.13) in comparison with NC-IVF. Miscarriage rate did not differ between CC-NC-IVF and NC-IVF (aRR 0.95; 95% CI 0.57-1.57). CONCLUSION: Low-dose CC does not reduce pregnancy or live birth rate per transferred embryo. It can be used in infertility treatment without negatively affecting the endometrium and implantation.

Gonadotropin Stimulation Reduces the Implantation and Live Birth Rate but Not the Miscarriage Rate of Embryos Transferred When Compared to Unstimulated In Vitro Fertilization.

Research suggests that gonadotropin stimulation in in vitro fertilization (IVF) treatment affects embryo quality and the endometrium that might influence embryo implantation, placentation and establishment of a viable pregnancy. We assessed the impact of gonadotropin stimulation on implantation, live birth and miscarriage rates per transferred embryo by comparing stimulated and unstimulated IVF treatment. In a cohort of 728 couples, 1310 IVF cycles with successful embryo transfer were analysed; 857 cycles were stimulated with gonadotropins > 75 IU/day (333 poor responder < 4 oocytes; 524 normal responders), and 453 were unstimulated. In total, 1913 fresh cleavage-stage embryos were transferred. Zygote but no embryo selection was performed, and supernumerous zygotes were vitrified. The implantation rate was defined as number of sonographically detected amniotic sacs; live birth rate as number of children born per transferred embryo. Modified mixed effect Poisson regression was used to account for the dependency of cycles and embryos within the same women and the same transfer cycle. Adjustments were made for maternal age, parity, primary or secondary infertility and indication for IVF. Per transferred embryo, implantation rates (rate ratio (RR) 1.37; 95% CI 1.04-1.81; p = 0.028; aRR 1.42; 95% CI 1.10-1.84; p = 0.008) and live birth rates (RR 1.33; 95% CI 0.95-1.86; p = 0.093; aRR 1.38; 95% CI 1.01-1.88; p = 0.044) were higher in NC-IVF compared to cIVF normal responders. Miscarriage did not differ (RR 0.99; 95% CI 0.59-1.65; p = 0.965; aRR 0.90; 95% CI 0.52-1.53 p = 0.698). Similar results were obtained in poor responders. The study suggests an impact of gonadotropin stimulation on the implantation potential of embryos.