Ovarian hyperstimulation syndrome (OHSS): It is a clinical symptom complex associated with ovarian enlargement resulting from exogenous gonadotropin therapy. Symptoms may include abdominal pain and distension, ascitis, gastrointestinal problems, respiratory compromise, oliguria, hemoconcentration, and thromboembolism. These symptoms may develop during ovulation induction or in early pregnancies that were conceived through exogenous ovarian stimulation. Ref: Hoffman B.L., Schorge J.O., Schaffer J.I., Halvorson L.M., Bradshaw K.D., Cunningham F.G., Calver L.E. (2012). Chapter 20. Treatment of the Infeile Couple. In B.L. Hoffman, J.O. Schorge, J.I. Schaffer, L.M. Halvorson, K.D. Bradshaw, F.G. Cunningham, L.E. Calver (Eds), Williams Gynecology, 2e.