Pelvic organ prolapse complicating pregnancy is a rare clinical condition and its incidence is one in 10,000~15,000 deliveries. It is associated with multiparity, low socioeconomic status, inadequate perinatal care, maternal malnutrition, previous abdominal surgery, and weakness of pelvic muscular and connective tissue. It can cause cervical dystocia, which leads to cervical laceration, uterine rupture, maternal and fetal death. We experienced a case, first in Korea, of cervical swelling that developed during labor, prolapsed beyond the vaginal introitus and thus obstructed the birth canal. The patient underwent cesarean section and subsequently received MgSO₄ topical therapy and resulted in complete resolution. We report this case with a brief review of literature.