The effect of elective single blastocyst transfer and elective double cleavage- stage embryo transfer on clinical pregnancy and live birth rates in fresh cycles

More than one embryo transferred into the uterus is likely to result in higher clinical pregnancy and live birth rates, but can also result in a higher rate of multiple pregnancy and births. Single blastocyst transfer can significantly reduce the rate of multiple pregnancies. The present study analyzed a total of 2941 fresh transfer cycles, including 1548 SBT cycles and 1393 DET cycles. Clinical pregnancy, twin pregnancy and live birth rates of the two groups were compared. Overall, the rates of clinical pregnancy and live birth in the DET group were significantly higher than those in the SBT group (75.1% vs. 71.3%, P =0.020; 66.6% vs. 63.0%, P =0.041). A sensitive analysis showed that DET lifted the rates of clinical pregnancy and live birth for patients with aged less than 35 years (aOR 1.792, 95% CI 1.455-2.207; aOR 1.572, 95% CI 1.301-1.901) but not for patients with age 35 years and over (aOR 0.879, 95% CI 0.530-1.457; aOR 1.004, 95% CI 0.614-1.643). The twin pregnancy rate in the SBT group was significantly lower than that in the DET group at all ages (aOR 32.502, 95% CI 21.885-48.269; aOR 23.504, 95% CI 7.714-71.608). SBT can lead to acceptable clinical pregnancy and live birth rates compared with DET and significantly reduce the twin pregnancy rate.