Overview

The placenta is a structure that develops inside your uterus during pregnancy, providing oxygen and nutrition to and removing wastes from your baby. The placenta connects to your baby through the umbilical cord. In most pregnancies, the placenta attaches at the top or side of the uterus.

Placenta previa (pluh-SEN-tuh PREH-vee-uh) occurs when a baby's placenta partially or totally covers the mother's cervix — the outlet for the uterus. Placenta previa can cause severe bleeding during pregnancy and delivery.

If you have placenta previa, you might bleed throughout your pregnancy and during your delivery. Your health care provider will recommend avoiding activities that might cause contractions, including having sex, douching, using tampons, or engaging in activities that can increase your risk of bleeding, such as running, squatting, and jumping.

You'll need a C-section to deliver your baby if the placenta previa doesn't resolve.

Symptoms

Bright red vaginal bleeding without pain during the second half of pregnancy is the main sign of placenta previa. Some women also have contractions.

In many women diagnosed with placenta previa early in their pregnancies, the placenta previa resolves. As the uterus grows, it might increase the distance between the cervix and the placenta. The more the placenta covers the cervix and the later in the pregnancy that it remains over the cervix, the less likely it is to resolve.

When to see a doctor

If you have vaginal bleeding during your second or third trimester, call your doctor right away. If the bleeding is severe, seek emergency medical care.

Causes

The exact cause of placenta previa is unknown.

Risk factors

Placenta previa is more common among women who:

  • Have had a baby
  • Have scars on the uterus, such as from previous surgery, including cesarean deliveries, uterine fibroid removal, and dilation and curettage
  • Had placenta previa with a previous pregnancy
  • Are carrying more than one fetus
  • Are age 35 or older
  • Are of a race other than white
  • Smoke
  • Use cocaine

Complications

If you have placenta previa, your health care provider will monitor you and your baby to reduce the risk of these serious complications:

  • Bleeding. Severe, possibly life-threatening vaginal bleeding (hemorrhage) can occur during labor, delivery or in the first few hours after delivery.
  • Preterm birth. Severe bleeding may prompt an emergency C-section before your baby is full term.