Day 2 transfer in clinical ART.

Over the past 20 years, numerous techniques have enhanced assisted reproductive technology outcomes to help couples have >60,000 infants in the United States in 2008. Several different days for embryo transfers have been studied, but debate for the best timing of embryo transfer is still ongoing. With growing concern about multiple gestations and neonatal outcomes, early cleavage stage embryo transfer with novel embryo selection tools may be attractive to some patients and in vitro fertilization programs. In this review, we summarize clinical and basic studies relating to the timing of embryo transfer and highlight the possibilities of safe embryo transfer by combining advanced embryo screening tools with potentially high efficiency and low adverse effects on clinical outcome.