Clinical aspects of ovarian hyperstimulation syndrome

Ovarian hyperstimulation syndrome (OHSS) is characterized by massive transudation of protein-rich fluid (mainly albumin) from the vascular space into the peritoneal pleural and to a lesser extent to the pericardial cavities. The intensity of the syndrome is related to the degree of the follicular response in the ovaries to the ovulation inducing agents. OHSS is still a threat to every patient undergoing ovulation induction. The pathophysiology of OHSS is of extreme importance in the face of the increased use of ovulation induction agents as well as the development of sophisticated assisted reproductive techniques. The correlation found between plasma cytokine activities and the severity of OHSS suggests that plasma cytokines may be involved in the pathogenesis of OHSS and may serve as a means of monitoring the syndrome during the acute phase and throughout convalescence. The interactions between cytokine and non-cytokine mediators of the syndrome, such as the renin-angiotensin system and vascular endothelial growth factor were recently clarified. Awareness of possible mechanisms and factors in the pathophysiology of OHSS will hopefully provide opportunities to design specific treatment regimens effective for both prevention and treatment of this potentially fatal iatrogenic condition. Among IVF patients with severe and critical OHSS, pregnancy rates, multiple gestations, miscarriage, preterm premature rupture of the membranes, prematurity, and low birth weight rates are significantly higher than those reported previously for pregnancies after assisted conception. The incidence of other obstetrical complications, as well as congenital malformations and Cesarean section rates are not significantly different.