Day-5 fresh embryo transfer is associated with superior clinical outcomes in oocyte donation cycles compared with day-3 embryo transfer

Abstract

Objective Τo compare clinical outcomes between day-5 (D5ET) and day-3 (D3ET) fresh embryo transfer in oocyte donation cycles. Study design A retrospective analysis of prospectively collected cohort data was performed enrolling all participants in an oocyte donation program performed either D5ET or D3ET regarding the period from June 2006 to June 2018. Cycles were compared by the day of embryo transfer. Primary outcomes were the clinical pregnancy rate and live birth rate. Secondary outcomes were implantation rate, biochemical pregnancy rate, early miscarriage rate, and twin pregnancy rate. Outcomes were adjusted for covariates within study groups. Results A total of 8023 cycles meeting our inclusion criteria were analyzed. D5ET consisted of 4865 cycles and D3ET of 3158 cycles. The D5ET group had a significantly higher clinical pregnancy rate (p < .001), live birth rate (p = .004), implantation rate (p < .001), and twin pregnancy rate (p = .02) than the D3ET group. Accordingly, biochemical pregnancy rate (7.4% vs. 5.1%, p < .001) and early miscarriage rate (4.1% vs. 3.2%, p = .04) were significantly higher in D3ET compared to the D5ET group. Conclusion Οocyte donation cycles with fresh D5ET resulted in fewer embryos transferred, higher clinical pregnancy rates, and higher live birth rates compared to D3ET. Our findings are strongly favoring day-5 embryo transfer in oocyte donation cycles.