Modern classification of the ovarian hyperstimulation syndrome

Ovarian hyperstimulation syndrome (OHSS) is the gravest complication of so-called controlled (far too often uncontrolled) ovarian hyperstimu­ lation (COH)1. From a perspective of priorities in reproductive medicine in general, and assisted reproductive technologies in particular, OHSS is second only to high-order multiple birth on the list of adverse outcomes which need to be mini­ mized or completely eliminated.