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@NEJM Ask the Authors & Experts: Fresh versus Frozen Embryos for Infertility in Polycystic Ovary Syndrome

Original Article

Fresh versus Frozen Embryos for Infertility in Polycystic Ovary Syndrome

Zi-Jiang Chen, M.D., Ph.D., Yuhua Shi, M.D., Ph.D., Yun Sun, M.D., Ph.D., Bo Zhang, M.D., Xiaoyan Liang, M.D., Ph.D., Yunxia Cao, M.D., Ph.D., Jing Yang, M.D., Ph.D., Jiayin Liu, M.D., Ph.D., Daimin Wei, M.D., Ph.D., Ning Weng, M.D., Lifeng Tian, M.D., Ph.D., Cuifang Hao, M.D., Ph.D., Dongzi Yang, M.D., Ph.D., Feng Zhou, M.M., Juanzi Shi, M.D., Ph.D., Yongle Xu, M.D., Jing Li, M.D., Junhao Yan, M.D., Ph.D., Yingying Qin, M.D., Ph.D., Han Zhao, M.D., Ph.D., Heping Zhang, Ph.D., Richard S. Legro, M.D.

Fresh embryo transfer is generally preferred over frozen embryo transfer for in-vitro fertilization (IVF), but some evidence suggests that frozen embryo transfer may improve livebirth rate and lower the rates of ovarian hyperstimulation syndrome and pregnancy complications in women with polycystic ovary syndrome.

We performed a multicenter trial in which 1508 infertile patients with polycystic ovary syndrome undergoing their first IVF cycle were randomized to fresh embryo transfer or embryo cryopreservation followed by frozen embryo transfer. After standardized ovarian stimulation, women underwent day-3 fresh or frozen embryo transfer of up to 2 embryos. The primary outcome was livebirth after the first embryo transfer cycle. 

As compared with fresh embryo transfer, frozen embryo transfer resulted in a higher frequency of livebirth after the first cycle [49.3%vs.42.0%, P=0.004; Rate Ratio:1.17, 95% Confidence intervals(CI):1.05 to 1.31]. The frozen embryo transfer group had lower frequencies of pregnancy loss (24.0%vs.30.7%, P=0.02; Rate Ratio:0.78, 95% CI:0.64 to 0.96) and ovarian hyperstimulation syndrome (1.3%vs.7.1%, P<0.001; Rate Ratio:0.19, 95%CI:0.10 to 0.37), but a higher frequency of pre-eclampsia (4.4%vs1.4%, P=0.009; Rate Ratio:3.12, 95%CI:1.26 to 7.73)],. Rates of other pregnancy and neonatal complications did not differ significantly between groups. There were 5 neonatal deaths in the frozen embryo transfer group, versus none in the fresh group (P = 0.06).

As compared with fresh embryo transfer, women with PCOS randomized to frozen embryo transfer had a higher rate of livebirth and a lower risk of ovarian hyperstimulation syndrome but an increased risk of pre-eclampsia. (Funded by National Basic Research Program of China (973 Program) and others; ClinicalTrial.gov number, NCT01841528)

 Originally Appeared in The New England Journal of Medicine on August 10, 2016.

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