A reaction to gonadotropins in which a woman’s ovaries become enlarged and produce an overabundance of eggs. Blood hormone levels rise, fluid may collect in the lungs or abdominal cavity, and cysts on the ovaries may rupture, causing internal bleeding. Blood clots sometimes develop. Symptoms include sudden weight gain and abdominal pain. Cycles stimulated with gonadotropins must be carefully monitored with ultrasound scans to minimize the occurrence of OHSS.