Pregnancy loss after frozen embryo transfer A comparison of three protocols

Frozen-embryo transfer in substituted cycles resulted in higher pregnancy rates but also increased pregnancy loss, leading to similar clinical pregnancy and delivery rates for the protocols studied.


Candido Tomás, M.D., Ph.D., Birgit Alsbjerg, M.D., Hannu Martikainen, M.D., Ph.D., Peter Humaidan, M.D., D.M.Sc.

Vol 98, Issue 5, Pages 1165-1169



To compare the reproductive outcome of three protocols for frozen embryo transfer treatment.


Retrospective follow-up study.


Two public clinics and one private clinic.


Four thousand four hundred seventy frozen ET cycles between 2006 and 2010.


Thawing of embryos and embryo transfer.

Main Outcome Measure(s):

Pregnancy test rate, clinical pregnancy rate, and pregnancy loss rate.


The natural cycle followed by P (NC + P) was used in 26% of cycles, the natural cycle with hCG (NC + hCG) in 10%, and the substituted cycle with estrogen and P (E + P) in 64% of cycles. The rate of transfers after thawing was similar in all groups (87.2%, 73.9%, and 87.2%, respectively). There was a significantly higher positive pregnancy test rate in the E + P (34.3%) and NC + hCG (35.5%) cycles as compared with the NC + P cycles (26.7%). However, the clinical pregnancy rate was similar in all groups (27.7%, 29.1%, and 24.3%, respectively). Moreover, no differences were seen between groups regarding the live-birth rate (20.1%, 23.5%, and 20.7%, respectively). A logistic regression analysis showed that the type of protocol was the only predictor of pregnancy loss, while age, irregular cycles, endometrial thickness, number, and quality of embryos transferred did not correlate to pregnancy loss.


A higher positive pregnancy test rate was obtained in E+P FET cycles in comparison to other protocols; however, due to an increased preclinical and clinical pregnancy loss, comparable clinical pregnancy and delivery rates are reported for the three protocols.

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