Immediate frozen embryo transfer improves pregnancy, live birth rates
Women who underwent immediate frozen-thawed embryo transfer (FET) following a stimulated in vitro fertilization (IVF) cycle were more likely to have ongoing pregnancy and live birth compared with those who underwent delayed FET, according to a study presented at ESHRE 2019.
“Immediate FET following a stimulated IVF cycle had a significantly higher ongoing pregnancy rate than delayed FET. The findings of the study support immediate FET after a failed fresh ET cycle or a freeze all cycle,” said study author Dr He Li from Shanghai Ji Ai Genetics and IVF Institute, Obstetrics and Gynecology Hospital, Fudan University in Shanghai, China.
The researchers conducted a study involving 724 women (aged ≤43 years) from Shanghai and Hong Kong who were randomized to undergo either immediate FET (n=362; FET performed in the first cycle) or delayed FET (n=362; FET performed in the second cycle) after a failed stimulated IVF cycle between August 2017 and December 2018. All FETs were performed in hormonal replacement cycles. [ESHRE 2019, abstract O-068]
In the intention-to-treat (ITT) analysis, women who underwent immediate FET had a significantly higher rate of ongoing pregnancy than those who had delayed FET (47.2 percent vs 39.2 percent, relative risk [RR], 0.72, 95 percent confidence interval [CI], 0.54–0.97; p=0.030), which exceeded the predefined equivalence margin of 10 percent.
A similar result was seen in the per-protocol analysis with a significantly higher rate of ongoing pregnancy among women in the immediate FET group compared with the delayed FET group (49.6 percent vs 41.5 percent, RR, 0.72, 95 percent CI, 0.53–0.98; p=0.034).
In addition, women in the immediate FET group had an increased live birth rate than those in the delayed FET group (39.5 percent vs 31.5 percent, odds ratio, 0.70, 95 percent CI, 0.52–0.96). However, the number of live births among 56 women are still pending, said Li.
Significantly fewer miscarriages occurred among women who had immediate FET compared with delayed FET (11.2 percent vs 19.7 percent, RR, 1.95, 95 percent CI, 1.09–3.47; p=0.022 for both ITT and per-protocol analyses).
All other pregnancy outcomes, such as positive hCG level, implantation rate, and clinical and multiple pregnancies, were comparable between the immediate and delayed FET groups for both ITT and per-protocol analyses.“FET has become an increasingly important part of IVF, but there is still no good evidence to support when to perform FET following a stimulated IVF cycle. Since all published studies are retrospective and the findings are contradictory, a randomized study [was] needed to provide level one evidence to guide the clinical practice,” said Li.