Patient and cycle characteristics predicting high pregnancy rates with single-embryo transfer: an analysis of the Society for Assisted Reproductive Technology outcomes between 2004 and 2013

To analyze factors associated with high live birth rate and low multiple birth rate in fresh and frozen–thawed assisted reproductive technology (ART) cycles. Retrospective cohort analysis. Not applicable. The study population included 181,523 women undergoing in vitro fertilization with autologous fresh first cycles, 27,033 with fresh first oocyte donor cycles, 37,658 with fresh second cycles, and 35,446 with frozen–thawed second cycles. None. Live birth rate and multiple birth rate after single-embryo transfer (SET) and double embryo transfer (DET) were measured, in addition to cycle characteristics. In patients with favorable prognostic factors, including younger maternal age, transfer of a blastocyst, and additional embryos cryopreserved, the gain in the live birth rate from SET to DET was approximately 10%–15%; however, the multiple birth rate increased from approximately 2% to greater than 49% in both autologous and donor fresh and frozen–thawed transfer cycles. This study reports a 10%–15% reduction in live birth rate and a 47% decrement in multiple birth rate with SET compared with DET in the setting of favorable patient prognostic factors. Our findings present an opportunity to increase the rate of SET across the United States and thereby reduce the multiple birth rate and its associated poor perinatal outcomes with assisted reproductive technology pregnancies.