Outcomes
PRETERM BIRTH, SECONDARY, MISCARRIAGE, EARLY PREGNANCY
The primary outcome of the present study was ongoing pregnancy, defined as the process of pregnancy beyond 12th week of gestation. The secondary outcomes included biochemical pregnancy: hCG test was positive after 12 (blastocyst) or 14 (cleaved embryo) days of transfer, clinical pregnancy (CP): the presence of intrauterine sac on ultrasound at six weeks of gestation, early pregnancy loss: spontaneous miscarriage before 12 weeks of pregnancy or no gestational sac was confirmed after biochemical pregnancy, multiple pregnancy: more than one gestational sac or embryo bud detected on ultrasound at 6-8 weeks of gestation and preterm birth: a baby born alive at 24-37 weeks of gestational age. At the present stage, we have already obtained the live birth data (defined as the delivery of a live baby at more than 24 weeks of gestation). As the live birth rate is the most concerned outcome for both patients and physicians, we also reported the live birth outcome as one of the secondary outcomes.All participants received allocated intervention and their follow-up data were all acquired in the present study.