Frozen-thawed embryo transfer is associated with a significantly reduced incidence of ectopic pregnancy

Abstract

To compare the incidence of ectopic pregnancy (EP) after fresh ET and thawed ET. Retrospective cohort study. Private fertility center. This retrospective study included 2,150 blastocyst transfers, including all 1,460 fresh autologous blastocyst transfers and all 690 transfers of autologous blastocysts derived from post-thaw extended culture of thawed bipronuclear oocytes in the 8-year study period 2004-2011. None. Visualized EP and treated persistent pregnancy of unknown location. The rate of visualized EP was 1.5% in pregnancies in fresh autologous cycles, which was significantly more than the rate of 0 with autologous post-thaw extended culture. The rates of treated persistent pregnancy of unknown location were 2.5% and 0.3% in these two groups, respectively, a difference that was also statistically significant (relative risk 7.3, 95% confidence interval 1.7-31.0). Relative to fresh transfer, thawed ET was associated with significantly reduced incidence of EP. These findings are consistent with ovarian stimulation increasing the risk of EP.