Study design and patients
This retrospective cohort study includes 41546 women who underwent fresh or frozen-thawed embryo transfer between January 2014 and December 2019 in the Center for Assisted Reproductive Technology of Northwest Women’s and Children’s Hospital, China. All the patients were followed up for one year after embryo transfer. The study protocol was approved by the ethics committee of Northwest Women’s and Children’s Hospital (No. 2019013). Because of the retrospective character of the study, informed consent was waived. Patient data were anonymized. Women who underwent the first cycle of fresh or frozen-thawed embryo transfer (FET) were eligible to participate. We excluded women with no embryo transferred. The women were divided into four educational categories according to the level of education received (elementary school graduate or less, middle school graduate, high school graduate, college graduate or higher).