Abstract
BACKGROUND: To evaluate the effect of elective single blastocyst transfer (eSBT) and elective double cleavage-stage embryo transfer (eDET) on clinical pregnancy and live birth rates in fresh cycles. METHODS: This retrospective study analyzed a total of 2941 fresh transfer cycles, including 1548 eSBT cycles and 1393 eDET cycles. Clinical pregnancy, twin pregnancy and live birth rates of the two groups were compared. RESULTS: Overall, the rates of clinical pregnancy and live birth in the eDET group were significantly higher than those in the eSBT group (75.1% vs. 71.3%, P = 0.019; 66.6% vs. 63.0%, P = 0.039). It was shown that eDET lifted the rates of clinical pregnancy and live birth for patients aged less than 35 years (aOR 1.783, 95% CI 1.451-2.191; aOR 1.508, 95% CI 1.262-1.803) but not for patients age 35 years and over (aOR 0.874, 95% CI 0.538-1.421; aOR 1.036, 95% CI 0.638-1.682). The twin pregnancy rate in the eSBT group was significantly lower than that in the eDET group at all ages (aOR 32.116, 95% CI 21.758-47.404; aOR 14.325, 95% CI 5.449-37.657). CONCLUSION: Compared with eDET, eSBT achieves clinically acceptable pregnancy and live birth rates while drastically reducing the risk of twin pregnancy in fresh cycles. It is generally recommended that infertile couples undergo eSBT during fresh cycles when possible, especially for females aged 35 years and over.