Frozen-Thawed Embryo Transfer Cycles Have a Lower Incidence of Ectopic Pregnancy Compared With Fresh Embryo Transfer Cycles.

OBJECTIVE

To evaluate the risk of ectopic pregnancy of embryo transfer.

DESIGN

A retrospective cohort study on the incidence of ectopic pregnancy in fresh and frozen-thawed embryo transfer cycles from January 1, 2010, to January 1, 2015.

PATIENTS

Infertile women undergoing frozen-thawed transfer cycles or fresh transfer cycles.

INTERVENTION

In-vitro fertilization, fresh embryo transfer, frozen-thawed embryo transfer, ectopic pregnancy.

MAIN OUTCOME MEASURES

Ectopic pregnancy rate and clinical pregnancy rate.

RESULT

A total of 69 756 in vitro fertilization-embryo transfer cycles from 2010 to 2015 were analyzed, including 45 960 (65.9%) fresh and 23 796 (34.1%) frozen-thawed embryo transfer cycles. The clinical pregnancy rate per embryo transfer was slightly lower in fresh embryo transfer cycles compared with frozen-thawed embryo transfer cycles (40.8% vs 43.1%, P < .001). Frozen-thawed embryo transfer is associated with a lower incidence of ectopic pregnancy per clinical pregnancy, compared with fresh embryo transfers (odds ratio = 0.31; 95% confidence interval = 0.24-0.39). Female age and body mass index have no influence on ectopic pregnancy. In the frozen-thawed embryo transfer cycles, blastocyst transfer shows a significantly lower incidence of ectopic pregnancy (0.8% vs 1.8%, P = .002) in comparison with day 3 cleavage embryo transfer.

CONCLUSION

The risk of ectopic pregnancy is lower in frozen-thawed embryo transfer cycles than fresh embryo transfer cycles, and blastocyst transfer could further decrease the ectopic pregnancy rate in frozen-thawed embryo transfer cycles.