Third trimester torsion of persistent ovarian cyst following ovarian hyperstimulation--an unusual cause of preterm labor.

Herein, a patient being operated for cesarean section due to preterm labor in the 31st week of a triplet pregnancy induced by gonadotropins is being described. On celiotomy, peritoneal effusion was present secondary to torsion of a 10 x 6 cm right ovarian cyst. This uncommon finding contradicts the common belief that the chances for an ovarian cyst in the overcrowded peritoneal space due to a 40-week-size uterus to twist around its pedicle are remote. The possibility that preterm labor was initiated by the torsion is discussed.