Two-blastocyst transfer has similar pregnancy rates and a decreased multiple gestation rate compared with three-blastocyst transfer.

OBJECTIVE: To examine the effect of the number of blastocysts transferred on pregnancy and multiple gestation rates.
DESIGN: Retrospective study.
SETTING: Academic infertility center. PATIENT(S): Patients < 40 years undergoing IVF, with FSH levels of < 15 mIU/mL and more than three eight-cell embryos. INTERVENTION(S): Embryos were cultured in P1 until day 3 and then transferred to blastocyst medium. A maximum of three blastocysts were transferred. MAIN OUTCOME MEASURE(S): Pregnancy, multiple gestation, and implantation rates. RESULT(S): All 55 patients developed blastocysts and underwent ET. Twenty-four patients had three embryos transferred and 29 patients had two embryos transferred. Two patients had only one embryo each for transfer. There was no difference in the viable pregnancy rate between the two-blastocyst transfer and three-blastocyst transfer groups (62% vs. 58%). In the two-blastocyst transfer group, 39% of pregnancies were multiple gestations (all twin gestations), compared with 79% of pregnancies in the three-blastocyst transfer group (50% twin gestations, 29% triplet gestations). The implantation rate was 47% in both groups. CONCLUSION(S): A commercially available, sequential culture system is highly effective for producing viable blastocysts. Two-blastocyst transfer eliminated the risk of triplets while maintaining the same high success rates seen with three-blastocyst ET.