Identification of the high-risk patient for ovarian hyperstimulation syndrome

Ovarian hyperstimulation syndrome (OHSS), an iatrogenic complication of ovarian stimulation for assisted reproduction, is a potentially life-threatening condition. Exogenous human chorionic gonadotropin (hCG) administered for final oocyte maturation and endogenous hCG produced by a developing pregnancy are fundamental in the development of the disease. Vascular endothelial growth factor is the key molecule mediating the pathophysiology of the syndrome, and genetic predisposition might play a role. Because the most severe cases are usually the late OHSS cases that occur when a pregnancy is established, several predictive markers have been introduced to identify the high-risk patient profile and consequently develop preventive strategies. This article reviews the most recent evidence evaluating the accuracy of different OHSS prediction parameters. Stratification was attempted according to the phase of the ovarian stimulation that the patients undergo. Anti-Müllerian hormone and the number of follicles seen on ultrasound seem promising discriminating factors, whereas prediction models that include age, antral follicle count, and estrogen levels on the day of ovulation triggering provide variable sensitivity and specificity. Until reliable genetic tests are available, and considering that the occurrence of pregnancy is unpredictable, the use of prognostic factors will be mainly indicative of risk rather than preventive of OHSS.