Objective: To determine the most critical factor on day-2, day-3, and day-S of embryo transfer in correlation with pregnancy rates. Method: This research is a retrospective study in Aster Fertility Clinic, IVF program- Dr. Hasan Sadikin Hospital, Bandung, Indo¬nesia. One hundred ninety five women enrolled in an IVF program conducted from March 2006 through November 2009 at the Aster Fertility…