Transfer of Fresh Versus Frozen Embryos in Ovulatory Women

A previous randomized controlled trial involving women with polycystic ovary syndrome (PCOS) compared fresh-embryo transfer with elective freezing of all embryos followed by frozen-embryo transfer. The data showed that frozen-embryo transfer had a higher live-birth rate in these women compared with fresh-embryo transfer. Whether frozen-embryo transfer also increases live-birth rates among ovulatory women with infertility without PCOS is uncertain. This randomized controlled trial compared the effects of frozen-embryo transfer and fresh-embryo transfer on live-birth rates and maternal and neonatal complications among ovulatory women. All women were undergoing their first cycle of in vitro fertilization (IVF). Up to 2 cleavage-stage embryos from the embryo culture were transferred. The primary study outcome was live-birth rates after the first transfer (fresh-or frozen-embryo transfer). There was no significant difference in the live-birth rate between the frozen-embryo group and the fresh-embryo group (48.7% and 50.2%, respectively; the relative risk was 0.97, with a 95% confidence interval of 0.89-1.06; P = 0.50). The rates of implantation, clinical pregnancy, ongoing pregnancy, and overall pregnancy loss also did not differ significantly in the 2 groups. The risk of ovarian hyperstimulation syndrome was significantly lower with frozen-embryo transfer compared with fresh-embryo transfer (0.6% vs 2.0%; relative risk, 0.32; 95% confidence interval, 0.14-0.74; P = 0.005). No significant differences were found in risks of obstetric and neonatal complications and other adverse outcomes. These data show no significant difference in live-birth rates between frozen-embryo transfer and fresh-embryo transfer among ovulatory women with infertility. However, the risk of ovarian hyperstimulation syndrome was lower with frozen-embryo transfer.