OBJECTIVETo compare the pregnancy and obstetric outcomes in elective single versus two cleavage-stage embryo transfer.

METHODSFresh cleavage-stage embryo transfer cycles between January, 2014 and October, 2015 were reviewed, including 39 single embryo transfer (eSET) cycles and 200 double embryo transfer (DET) cycles. The clinical pregnancy rates, implantation rates, multiple pregnancy rates, live birth rate, and obstetric outcomes (gestational age, preterm delivery rate and mean birth weight) were compared between the two groups.

RESULTSThe baseline characteristics were comparable between the two groups. The estradiol level on the day of trigger and the oocyte number were significantly higher in eSET group than in DET group (10654.4 pmol/L vs 8284.2 pmol/L and 8.4 vs 7.0, respectively). No significant difference was found in the pregnancy rate (56.4% vs 66.0%) or live birth rate (48.7% vs 51.5%) between the two groups, and their implantation rates differed significantly (56.4% vs 37.8%). No multiple pregnancies occurred in eSET group while the rate of multiple pregnancies was 22.7% in DET group. The gestational age and mean birth weight were significantly higher in eSET group (P<0.05), and the preterm delivery rate after DET was nearly three times of that after eSET, although this difference was not statistically significant.

CONCLUSIONSElective single embryo transfer can be performed without compromising the live birth rates. Multiple pregnancy rates can be significantly reduced with eSET, which also results in a higher chance of delivering a term singleton live birth compared with DET.