High estradiol levels in fresh embryo transfer cycles are not associated with detrimental impact on birth outcomes.

PURPOSE: There is an unclear relationship between estradiol levels and fresh embryo transfer (ET) outcomes. We determined the relationship between estradiol on the day of trigger, in fresh ET cycles without premature progesterone elevation, and good birth outcomes (GBO). METHODS: We identified autologous fresh ET cycles from 2015 to 2021 at multiple clinics in the USA. Patients with recurrent pregnancy loss, uterine factor, and elevated progesterone on the day of trigger (progesterone > 2 ng/mL or 3-day area under the curve > 4.5 ng/mL) were excluded. The primary outcome was GBO (singleton, term, live birth with appropriate weight). Log-binomial generalized estimating equations determined the likelihood of outcomes. RESULTS: Of 17,608 fresh ET cycles, 5025 (29%) yielded GBO. Cycles with estradiol ≥ 4000 pg/mL had a greater likelihood of GBO compared to cycles < 1000 pg/mL (aRR = 1.32, 95% CI 1.13-1.54). Pairwise comparisons of estradiol between < 1000 pg/mL versus 1000-1999 pg/mL and 1000-1999 pg/mL versus 2000-2999 pg/mL revealed a higher likelihood of GBO with higher estradiol (aRR 0.83, 95% CI 0.73-0.95; aRR 0.91, 95% CI 0.85-0.97, respectively). Comparisons amongst more elevated estradiol levels revealed that the likelihood of GBO remained similar between groups (2000-2999 pg/mL versus 3000-3999 pg/mL, aRR 1.04, 95% CI 0.97-1.11; 3000-3999 pg/mL versus ≥ 4000 pg/mL, aRR 0.96, 95% CI 0.9-1.04). CONCLUSION: In fresh ET cycles, higher estradiol levels were associated with an increased prevalence of GBO until estradiol 2000-2999 pg/mL, thereafter plateauing. In fresh ET candidates, elevated estradiol levels should not preclude eligibility though premature progesterone rise, and risk of ovarian hyperstimulation syndrome must still be considered.

Impact of time interval from cesarean delivery to frozen embryo transfer on reproductive and neonatal outcomes.

OBJECTIVE: To evaluate differences in reproductive and neonatal outcomes on the basis of the time interval from cesarean delivery to subsequent frozen embryo transfer (FET). DESIGN: Retrospective cohort. SETTING: Multicenter fertility practice. PATIENTS: Women undergoing autologous elective single embryo transfer FET after prior cesarean delivery. INTERVENTION: Time from prior cesarean delivery to subsequent FET. MAIN OUTCOME MEASURES: live birth (LB). RESULTS: A total of 6,556 autologous elective single embryo transfer FET cycles were included. Frozen embryo transfer cycles were divided into eight groups on the basis of the time interval from prior cesarean delivery to subsequent FET in months. A secondary analysis was then performed with time as a continuous variable. The proportion of LBs did not differ significantly across all time interval groups and over continuous time (range: 40.0%-45.6%). The mean gestational age at the time of delivery did not significantly differ as the time between prior cesarean delivery and subsequent FET increased (range: 37.3-38.4). When time was evaluated continuously, the proportion of preterm births was higher with a shorter time between cesarean delivery and subsequent FET. The mean birth weight ranged from 3,181-3,470g, with a statistically significant increase over time. However, the proportions of extremely low birth weight, very low birth weight, and low birth weight did not significantly differ. CONCLUSION: There were no significant differences in reproductive outcomes on the basis of the time interval from cesarean delivery to FET, including LB. The proportion of preterm deliveries decreased with a longer time between cesarean delivery and FET. Differences in mean neonatal birth weight were not clinically significant because the proportion of low birth weight neonates was not significantly different over time. Although large, this sample cannot address all outcomes associated with short interpregnancy intervals, particularly rarer outcomes such as uterine rupture. When counseling patients, the timing of FET after cesarean delivery must be balanced against the risks of increasing maternal age on reproductive and neonatal outcomes.