The impact of the day of embryo transfer and type of transfer cycle on the incidence of ectopic pregnancy following IVF

Abstract

Tubal disease and history of pelvic infection have been shown to increase the incidence of ectopic pregnancy (EP) following IVF. However, there is inconsistent data on the impact of the day of embryo transfer and type of transfer cycle (fresh versus frozen) on the EP rate. Therefore, we aim to compare the EP rate between fresh and frozen cycles and between day 3 and day 5 transfers. Retrospective cohort study. Patients who achieved pregnancy following autologous fresh or frozen-thawed embryo transfer (FET) cycles between January 2004 and December 2015 were included. EP rate was compared between fresh and frozen cycles and between day 3 and day 5 transfers. χ2 test and Fisher’s exact test were used as appropriate. Odds ratio (OR) with 95% confidence intervals (CI) were calculated and adjusted for confounders. A total of 12,841 fresh and 3,997 FET cycles were included. The transfer of ≥ 2 embryos was associated with a significantly higher EP rate compared to the transfer of one embryo (1.5% vs. 0.7%, respectively; p=0.001). Fresh cycles were associated with a significantly higher EP rate compared to FET cycle (1.6% vs. 0.7%; p<0.001). The odds ratio remained significant after controlling for the number transferred embryos and history of tubal disease (aOR = 2; 95% CI = 1.3-3.1). Within fresh cycles, day 3 and day 5 transfers were associated with comparable EP rate (1.7% vs 1.3%, respectively; p=0.2). Likewise, within FET cycles, there was no significant difference between day 3 and day 5 transfers (1.2% vs. 0.6%, respectively; p=0.2). Among the four groups, EP rate following day 5 FET (0.6%) was significantly lower than day 3 fresh (1.7%, p<0.001) and day 5 fresh (1.3%, p=0.005) transfers. Day 5 FET is associated with a lower EP rate compared to day 3 and day 5 fresh embryo transfer cycles in patients undergoing IVF. Additionally, the transfer of a higher number of embryos is associated with greater incidence of EP.