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.

The exact cause of placenta previa is unknown.

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

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.