GNRH1 and ovarian hyperstimulation syndrome: The proportion of patients at high risk for OHSS who developed moderate early OHSS was 27.9 % (12/43), 29.4 % (15/51), 33.3 % (13/39), 25.0 % (8/28), and 27.5 % (33/120) in the letrozole group, mifepristone group, GnRH-ant group, three-drug group, and control group, respectively.