Qualified patients will be randomized into either of two groups. Group A will undergo a fresh embryo transfer after ovarian stimulation, and group B will have all of their embryos cryopreserved after ovarian stimulation and then undergo a frozen–thawed embryo transfer. All of the participants will receive a standardized gonadotropin-releasing hormone (GnRH) antagonist ovarian stimulation protocol and luteal phase support.
At 12 weeks gestation, the presence of first-trimester pregnancy complications (OHSS, miscarriage, ectopic pregnancy and/or gestational trophoblastic disease) will be evaluated by inspecting medical records and will be recorded by completing the case report form for the first pregnancy follow-up time point.
At 28 weeks gestation, the second-trimester pregnancy complications (prenatal diagnosis test results, abortion, gestational diabetes, preeclampsia/eclampsia, incompetent cervix, premature rupture of membrane and/or placenta abruption) will be followed up by telephone call to complete the second pregnancy follow-up time point.
At 37 weeks gestation, the third-trimester pregnancy complications (preterm labor, placenta abruptio, placenta accreta, placenta previa, preeclampsia/eclampsia, intrauterine growth retardation, premature rupture of membrane and/or abnormality of amniotic fluid) will be followed up by telephone call to complete the third pregnancy follow-up time point.
Participants will be required to notify investigators of the time of delivery. An investigator will be sent to the delivery hospital, and placental and cord blood samples will be collected. The delivery information (gestational age, delivery mode, placenta abnormality and/or delivery complications), infant information (for example, birth weight, birth defect) will be recorded by completing forms designed for this fourth follow-up pregnancy visit. The obstetric medical record will be copied, if possible, for the study chart source documents.
At 6 weeks after delivery, postpartum information regarding complications of the mother (for example, postpartum depression, infection, late postpartum hemorrhage) and the infant (for example, neonatal respiratory distress syndrome, neonatal jaundice, neonatal infection, neonatal death, neonatal hospitalization) will be followed up by telephone call for the fifth and final follow-up time point.
If a live birth is not achieved and there are surplus cryopreserved embryos from the first IVF cycle, we will track the outcomes of all frozen embryo transfers in both groups A and B.