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

Abstract

Objective: To compare the incidence of ectopic pregnancy (EP) after fresh ET and thawed ET.

Design: Retrospective cohort study.

Setting: Private fertility center.

Patient(s): 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.

Intervention(s): None.

Main outcome measure(s): Visualized EP and treated persistent pregnancy of unknown location.

Result(s): 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).

Conclusion(s): 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.