Prevention and treatment of ovarian hyperstimulation syndrome.

Ovarian hyperstimulation syndrome (OHSS) is the most serious complication of ovarian stimulation. Although the milder form is more common, particularly among patients undergoing gonadotropin stimulation for assisted reproductive technology, the severe form is rare. Classification schemes are clinically directed and useful in diagnosis and management of moderate and severe cases. The ovarian renin-angiotensin system, as well as vascular endothelial growth factor (VEGF)/vascular permeability factor (VPF) offers attractive theories as to the pathogenesis of this disorder. Unfortunately, clinical applications of these findings are not yet available. Possible prevention measures would include identification of patients at high risk, withholding human chorionic gonadotropin (hCG), using a gonadotropin-releasing hormone agonist to trigger ovulation, using a smaller dose of hCG, controlled gonadotropin drift, or avoidance of fresh embryo transfer by cryopreservation and frozen embryo transfer at a later date. Management of moderate to severe OHSS rests upon the principles of expanding intravascular volume and maintaining adequate urine output.