Pregnant Woman

Placenta previa is a condition that happens while a baby is growing in its mother’s womb (uterus). Around 2% of pregnancies are affected by this condition.

The placenta is a source of nutrients and oxygen for the baby, and removes waste from the baby’s blood.

During pregnancy, the placenta is usually attached inside and near the top or side of the mother’s womb. In placenta previa, the placenta is attached near the bottom of the womb. When the placenta attaches there, it can block the cervix (where the womb opens into the birth canal) partially or completely.

Placenta previa is a worrisome diagnosis. This page will help you understand how the condition affects a pregnancy.

Risk Factors for Placenta Previa

The causes of this condition are unknown. You may be at a higher risk if you:

  • Had placenta previa in a prior pregnancy (you have only a 5% chance of having it again)
  • Have ever had surgery, including a cesarean section (C-section), on your uterus
  • Are pregnant with more than one baby
  • Had a prior pregnancy
  • Are at least 35 years old
  • Smoke (no studies show how much it increases the risk)
  • Used cocaine during pregnancy (experts do not know how much this increases the risk)

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Symptoms of Placenta Previa

The main symptom is bleeding during pregnancy, especially after about 20 weeks. According to the March of Dimes, two-thirds (66%) of women with this condition will have bleeding. Some women may also have cramping or contractions.

Diagnosing Placenta Previa

This condition is often diagnosed during a routine ultrasound during pregnancy. If you experience bleeding or cramping, your doctor may recommend an ultrasound to rule out this condition.

Treating Placenta Previa

You should always alert your doctor if you experience any bleeding during pregnancy. There is no treatment for placenta previa, but there are things you can do before delivering your baby. Changes in behaviors or activities your doctor may recommend include:

  • Reducing physical activity (such as certain types of exercise)
  • Avoiding sexual intercourse
  • Avoiding the use of tampons or douching

You may also need to see your doctor more often during your pregnancy. The goal is to reduce the amount of bleeding and contractions you have, so that both you and the baby stay healthy.

Effects of Placenta Previa on a Pregnancy

The main symptom of this condition — bleeding — can be hard on both mother and baby. If you have heavy bleeding, you may need a blood transfusion.

With placenta previa, the placenta can be torn away from the wall of the uterus during delivery, causing heavy bleeding that may be life-threatening to both mother and baby.

Some cases of placenta previa correct themselves during pregnancy. If that doesn’t happen, your doctor will likely recommend delivering the baby by C-section before labor begins.

Near the end of your pregnancy, your doctor may recommend giving you corticosteroids to help the baby’s lungs develop. A procedure called an amniocentesis can let the doctor know if the baby’s lungs are developed enough for an earlier delivery.

Sources

Natural History of Placenta Previa in TWINS. Obstetrics & Gynecology. 2012. Link

Placenta Previa. March of Dimes. Link

Risk of placenta previa in second birth after first birth cesarean section: a population-based study and meta-analysis. BMC Pregnancy and Childbirth. 2011. Link

About UPMC Magee-Womens Hospital

For more than a century, UPMC Magee-Womens Hospital has provided high-quality medical care to women at all stages of life. UPMC Magee is long renowned for its services to women and babies, but also offers a wide range of care to men as well. Nearly 10,000 babies are born each year at Magee, and the hospital’s NICU is one of the largest in the country. The U.S. Department of Health and Human Services recognizes Magee as a National Center of Excellence in Women’s Health, and the Magee-Womens Research Institute is the largest research institute in the U.S. devoted exclusively to women’s health and reproductive biology.