-One to 6 percent pregnant women presents with ultrasound evidence of a placenta previa between 10 and 20 weeks of gestation. 90 percent of these early cases resolve.

-The characteristic symptom: Painless vaginal bleeding.

-Major risk factors: Previous placenta previa, previous cesarean delivery, multiple gestation, increasing maternal age, increasing parity, maternal smoking, cocaine use, infertility treatment.

-Placenta previa should be suspected in any woman beyond 20 weeks of gestation who presents with vaginal bleeding.

-Diagnosis is based on identification of placental tissue over the internal cervical os on ultrasound.

-Asymptomatic women: determine whether the previa resolves with increasing gestational age.  Follow-up transvaginal ultrasonography is performed at 32 weeks of gestation and again at 36 weeks if the placenta remains over or <2 cm from the internal os

-If previa persists at 36+0 to 37+6 weeks of gestation, perform cesarean delivery.