[Ovarian hyperstimulation syndrome].

Techniques of assisted fertilization are usually preceded by ovarian stimulation therapies. This implies the risk of development of an ovarian hyperstimulation syndrome (OHS). With this article, clinical relevance, possible pathogenetic mechanisms, diagnosis, therapy and prevention of OHS are discussed. In addition, three patients with severe OHS are presented. Valid parameters for OHS risk assessment are peripheral E2 values as well as number and diameter of follicles. Until now, the mechanisms which lead to severe OHS are unknown, but hCG seems to trigger the development of symptoms, as OHS very rarely occurs without prior hCG application. Symptoms of severe OHS comprise ovarian enlargement, fluid- and electrolyte imbalance, third space fluid accumulation, haemoconcentration and hypercoagulation. Only symptomatic therapy is available. The significance of vascular mediators for the development of OHS is discussed.