Comparison of Pregnancy Outcomes in Elective Single-Blastocyst Transfer Versus Double-Blastocyst Transfer Stratified by Age

Infants conceived through the use of in vitro fertilization (IVF) and assisted reproductive technology (ART) account for 1% of newborns in the United States. Advances in controlled ovarian hyperstimulation and cell culturing have achieved higher implantation rates and live birth rates. However, these procedures have led to marked increases in rates of multiple births. Risks associated with multiple gestations to both mother and fetus are the most common adverse outcomes associated with ART. With twin pregnancies, there is increased risk of preeclampsia, hypertension, preterm labor, preterm rupture of membranes, fetal death, and other adverse outcomes. Accordingly, reduction in the number of embryos transferred is a necessary measure to minimize the incidence of multiples in ART. Previous studies have shown that the rate of multiple births is substantially reduced with use of a single-embryo transfer (SBT) compared with a double embryo transfer (2BT) and does not compromise pregnancy outcomes. The multiple birth rate after IVF in Europe (26% [24% twins, 2% high-order multiples]) is significantly lower than in the United States (35% [31% twins, 4% high-order multiples]). The primary reason for this discrepancy is that the clinical practice of elective SBT (eSBT) is widely accepted in Europe as the standard of care, whereas SBT is generally uncommon in the United States. This retrospective study was designed to determine whether use of eSBT in American women <40 years of age who are undergoing fresh nondonor IVF cycles can significantly reduce their risk of multiple births and can do so without compromising their pregnancy rates. Data on pregnancy outcomes for IVF women were obtained from the database at a university IVF center. The pregnancy outcomes of women undergoing fresh nondonor oocyte IVF cycles of eSBT (n = 52 cycles) were compared with those of patients who had 2BT (n = 1086 cycles). Women in the eSBT group had a 12-fold reduction in the twinning rate compared with the 2BT group (25%-2%, P < 0.05). No statistically significant differences were found in pregnancy rates between the groups (eSBT group, 63% vs. 2BT group, 61%). The investigators conclude from these findings that increased use of eSBT in American women <40 years of age undergoing nondonor fresh IVF cycles can substantially reduce their risk of multiple births without any reduction in pregnancy rates.