gynecology and obstetrics
Placenta Previa
Introduction
Placenta previa is implantation of the placenta over or near the internal os of the cervix. It typically manifests as painless vaginal bleeding after 20 weeks gestation; the source of bleeding in placenta previa is maternal. Diagnosis is by ultrasonography. Treatment is modified activity if minor vaginal bleeding occurs before 36 weeks gestation, with cesarean delivery at 36 to 37 weeks/6 days. If bleeding is severe or refractory or if fetal status is nonreassuring, immediate cesarean delivery is indicated. Placenta previa refers to placental tissue that covers any portion of the internal cervical os. A placenta is termed low lying when the placental edge does not cover the internal os but is within 2 cm of it. Incidence of placenta previa is approximately 5/1000 deliveries ( General reference ). If placenta previa occurs during early pregnancy, it usually resolves by 28 weeks as the uterus enlarges. 