Measurements
Patient data were obtained from our centre records, included age, BMI, systolic blood pressure (SBP), diastolic blood pressure (DBP), duration and type of infertility, past medical history, a basic vaginal ultrasound, a basal hormone profile evaluation and outcomes of controlled ovarian hyperstimulation (COH), as well as laboratory and clinical features of FET cycles. Blood samples of a basal hormone profile were collected for assessment on days 2–5 of a spontaneous or progestin-induced menstrual cycle in all women. All the hormonal assays were performed in the laboratories of the Center for Reproductive Medicine, Cheeloo College of Medicine, Shandong University.