In this randomized trial involving infertile women with the polycystic ovary syndrome, frozen-embryo transfer was associated with a higher rate of live birth than was fresh-embryo transfer after the first transfer. In vitro fertilization (IVF) is widely performed as an infertility treatment and has resulted in the births of more than 5 million infants worldwide. 1 However, there are concerns about the safety of the procedures for women and for their infants. 1 , 2 The ovarian hyperstimulation syndrome (which is caused by ovarian enlargement, an increase in vascular permeability and abdominal ascites, and intravascular hemoconcentration) is a potentially life-threatening complication of ovarian stimulation. 3 Pregnancies conceived by means of IVF are associated with greater risks of maternal and neonatal complications, including preeclampsia, preterm delivery, low birth weight, and congenital anomalies, than are spontaneous pregnancies. . . .