In Vitro Fertilization with Single Blastocyst-Stage versus Single Cleavage-Stage Embryos

In this randomized trial in women under 36 years of age who were undergoing a first or second trial of in vitro fertilization, transfer of a single blastocyst-stage (day 5) embryo resulted in higher rates of pregnancy and delivery than transfer of a single cleavage-stage (day 3) embryo. Multiple gestation was rare. In women under 36 years of age who were undergoing a first or second trial of in vitro fertilization, transfer of a single blastocyst-stage (day 5) embryo resulted in higher rates of pregnancy and delivery than transfer of a single cleavage-stage (day 3) embryo. Although the first successful delivery after in vitro fertilization was achieved after the placement of one embryo, 1 the practice of single-embryo transfer was soon replaced by multifollicular ovarian stimulation followed by the transfer of multiple embryos. Transfer of multiple embryos results in higher pregnancy rates than single-embryo transfer, but multiple gestations are a common and serious complication of this approach. 2 , 3 The rate of multiple gestations after in vitro fertilization is 26.4 percent in Europe 4 and 35.3 percent in the United States, 5 as compared with 1.1 percent after natural conception. 6 Adverse outcomes associated with high-order gestations include serious perinatal morbidity . . .