IVF in PCOS: Are Frozen Embryos Better Than Fresh?

Summary and Comment |
August 10, 2016

IVF in PCOS: Are Frozen Embryos Better Than Fresh?

  1. Robert W. Rebar, MD

In a randomized trial, live-birth rates were higher and risk for ovarian hyperstimulation syndrome was lower following frozen-embryo transfer.

  1. Robert W. Rebar, MD

Women with polycystic ovary syndrome (PCOS) undergoing in vitro fertilization (IVF) have excess risk for ovarian hyperstimulation syndrome (OHSS) after fresh-embryo transfer. Investigators in China conducted a trial of fresh- versus frozen-embryo transfer to determine if use of frozen embryos would augment live-birth rates and lower risk for treatment-related complications in 1508 women (age range, 20–34) with PCOS undergoing their first IVF cycle. Participants were randomized to fresh-embryo transfer or embryo cryopreservation with transfer during a subsequent controlled cycle. After 3 days in culture, up to two fresh or frozen embryos were transferred.

Use of frozen embryos yielded higher live-birth rates after the first transfer than did fresh embryos (49% vs. 42%; rate ratio, 1.2; P=0.004), largely because rates of pregnancy loss were lower (22% vs. 33%; RR, 0.7; P<0.001). Moderate-to-severe OHSS was less likely in women undergoing frozen-embryo transfer (1% vs. 7%; RR, 0.2; P<0.001), but incidence of preeclampsia was higher (4% vs. 1%; RR, 3.1; P=0.009). Singleton infants in the frozen-transfer group weighed significantly more than those in the fresh group (3511 vs. 3349 g; P=0.005). Five neonatal deaths occurred in the frozen group and none in the fresh group (P=0.06); rates of other obstetric or neonatal complications did not differ between groups. When all frozen-embryo transfers within 12 months of the initial transfer were considered, cumulative live-birth rates were the same in both groups.


In showing that incidence of OHSS can be substantially reduced in a very high-risk group — women with PCOS — this study may represent another step toward eliminating OHSS and multiple pregnancies in IVF cycles. These embryos were cultured only to the cleavage stage (3 days), but pregnancy rates are higher following culture to the blastocyst stage (5 days; NEJM JW Womens Health Aug 8 2016; [e-pub] and Fertil Steril 2016 Jul 1; [e-pub]). As an editorialist notes, the higher rate of pregnancy loss in the fresh-embryo group may be attributable to embryo–endometrial dyssynchrony. These results justify a randomized trial of fresh versus frozen transfer of single blastocysts in an unselected population of infertile women undergoing IVF.

Editor Disclosures at Time of Publication

  • Disclosures for Robert W. Rebar, MD at time of publication Grant / Research support Religious, Ethical and Cultural Impacts on the Delivery of Reproductive Healthcare: A Program for InterProfessional Education (RECIPE; Co-Principal Investigator) from the Association of Professors of Gynecology (APGO) Education Foundation Editorial boards Contraception (Deputy Editor); EndoText (Section Editor); Clinical OB/GYN Alert (Associate Editor) Leadership positions in professional societies American Society for Reproductive Medicine (Member Practice Committee)


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