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 based on the time interval from cesarean delivery to subsequent frozen embryo transfer (FET) DESIGN: Retrospective cohort SUBJECTS: Women undergoing autologous elective single embryo transfer (eSET) FET following prior cesarean delivery EXPOSURE: Time from prior cesarean delivery to subsequent FET MAIN OUTCOME MEASURES: Live birth RESULTS: A total of 6,556 autologous eSET FET cycles were included. FET cycles were divided into eight groups based on the time interval from prior cesarean delivery to subsequent FET in months. Time was also evaluated as a continuous variable. The proportion of live births did not differ significantly across all time interval groups and over continuous time (range: 40.0% - 45.6%, adjusted (adj) p = 0.572, continuous adj p = 0.599). 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 weeks, adj p = 0.87, continuous adj p = 0.06). When time was evaluated continuously, the proportion of preterm births was higher with a shorter time between cesarean delivery and subsequent FET (p = 0.02). Mean birth weight ranged from 3181 grams to 3470 grams, with a statistically significant increase over time (continuous adj p = 0.01). 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 based on the time interval from cesarean delivery to FET, including live birth. 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, as the proportion of low-birth-weight neonates was not significantly different over time. While 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 following cesarean delivery must be balanced against the risks of increasing maternal age on reproductive and neonatal outcomes.