This was a prospective cohort study of all women attending the Center for Reproductive Medicine, Department of Gynecology and Obstetrics, Nanfang Hospital, affiliated with Southern Medical University for in vitro fertilization and/or intracytoplasmic sperm injection . Women at high risk of OHSS who received IVF and/or intracytoplasmic sperm injection (ICSI) treatment with a flexible GnRH antagonist protocol were recruited to participate in this study.