Symptoms and causes

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.
May 17, 2017
References
  1. Lockwood CJ, et al. Clinical manifestations and diagnosis, and course of placenta previa. http://www.uptodate.com/home. Accessed Feb. 3, 2017.
  2. Frequently asked questions. Pregnancy FAQ038. Bleeding during pregnancy. American Congress of Obstetricians and Gynecologists. http://www.acog.org/Patients/FAQs/Bleeding-During-Pregnancy. Accessed Feb. 3, 2017.
  3. Lockwood CJ, et al. Management of placenta previa. http://www.uptodate.com/home. Accessed Feb. 3, 2017.
  4. Placenta previa. March of Dimes. http://www.marchofdimes.org/complications/placenta-previa.aspx. Accessed Feb. 3, 2017.
  5. Placenta previa. Merck Manual Professional Version. http://www.merckmanuals.com/professional/gynecology-and-obstetrics/abnormalities-of-pregnancy/placenta-previa. Accessed Feb. 3, 2017.
  6. Butler Tobah YS (expert opinion). Mayo Clinic, Rochester, Minn. Accessed March 1, 2017.