Cumulative Live Birth Rates After Cleavage-stage Versus Blastocyst-stage Embryo Transfer

The aim of this RCT is to compare differences in the efficacy and safety between cleavage-stage embryo transfer and blastocyst-stage embryo transfer in IVF/ICSI treatment cycle, taking into account of subsequent vitrified embryo transfers. Subjects with 3 or more transferrable cleavage embryos will be randomized to the cleavage-stage or blastocyst-stage embryos transfer group. The primary outcome is cumulative live birth rate (CLBR) per patient until the first live birth from one initiated oocyte retrieval cycle, calculated using outcomes from the first three embryo transfers within 1 year after randomization.