Litzky JF, et al. - A comparison was performed of the effect of frozen/thawed vs fresh embryo transfer on birthweight outcomes for singleton, term infants conceived using in vitro fertilization in the United States between 2007 and 2014, including average birthweight and the risks of both macrosomia (>4000 grams) and low birthweight (<2500 grams). In comparison with fresh embryo transfer, frozen/thawed embryo transfer was associated with increased average birthweight in singleton, autologous oocytes, term infants born in the United States, with a significant interaction between frozen/thawed embryo transfer and infant sex. Following frozen/thawed embryo transfer, greater risk of macrosomia was observed compared to that following fresh embryo transfer. However, the risk of low birthweight among frozen/thawed embryo transfer infants was markedly lower than fresh embryo transfer infants.