Hyperreactio luteinalis associated with severe twin-to-twin transfusion syndrome.

Twin-to-twin transfusion syndrome (TTTS) is a severe complication of monochorionic twin pregnancies, with high perinatal loss and significant morbidity. The etiology of this syndrome remains unclear. Hyperreactio luteinalis is a rare benign condition characterized by maternal ovarian enlargement due to theca lutein cysts.