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

The incidence of pregnancy of unknown location and visualized EP were each significantly reduced in transfers of thawed embryos when compared with fresh embryo transfers.

Bruce S. Shapiro, M.D., Ph.D., Said T. Daneshmand, M.D., Laura De Leon, M.D., Forest C. Garner, M.Sc., Martha Aguirre, Ph.D., Cynthia Hudson, M.S.

Volume 98, Issue 6, Pages 1490-1494, December 2012


To compare the incidence of ectopic pregnancy after fresh embryo transfer and thawed embryo transfer.

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 (PTEC) of thawed bipronuclear oocytes in the 8-year study period 2004-2011.

Main outcome measures:
Visualized ectopic pregnancy (VEP) and treated persistent pregnancy of unknown location (TPPUL).

The rate of VEP was 1.5% in pregnancies in fresh autologous cycles, which was significantly greater than the rate of 0.0% with autologous PTEC. The rates of TPPUL were 2.5% and 0.3% in these two groups, respectively, a difference that was also statistically significant (relative risk 7.3, 95% CI 1.7-31.0).

Relative to fresh transfer, thawed embryo transfer was associated with significantly reduced incidence of ectopic pregnancy. These findings are consistent with ovarian stimulation increasing the risk of ectopic pregnancy.

  • Thank you very much Dr. Shapiro for this interesting paper. It is important to take into account methods to prevent this life-threatening condition. I have a couple of points I would like to raise. Firstly, did you study the previous ectopic pregnancies of the patients? Do you know if they were comparable in both study groups?. Secondly, regarding the embryo cleveage, do you think a D3 embryo transfer is associated with more risk of an ectopic pregnancy compared to a D5-6 ET?.

  • Micah Hill

    Thank you Dr. Shapiro for the very interesting paper. It was particularly noteworthy to see that the lower rate of ectopic pregnancies in FET cycles persisted in tubal factor infertility patients. As this study was retrospective and over a long period of time (8 years), I was curious if there were any major laboratory changes during the study period and if so, was the distribution of patients electing to freeze their embryos similar across the 8 year period?

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