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Placenta Previa - Topic Overview

What is placenta previa?

Placenta previa is a pregnancy problem in which the placenta blocks the cervix. The placenta is a round, flat organ that forms on the inside wall of the uterus soon after conception. During pregnancy, it gives the baby food and oxygen from the mother.

In a normal pregnancy, the placenta is attached high up in the uterus, away from the cervix. In placenta previa, the placenta forms low in the uterus camera.gif and covers all or part of the cervix.

If placenta previa is present during labor and delivery, it can cause problems for both mother and baby.

  • The mother may lose a lot of blood, which can be dangerous for both her and her baby.
  • The placenta may separate too early from the wall of the uterus. This is called placenta abruptio, and it can cause serious bleeding, too.
  • The baby may be born too early (premature), at a low birth weight, or with a birth defect.

What causes placenta previa?

Doctors aren't sure what causes this problem. But some things make you more likely to have it. These are called risk factors.

You can't control most risk factors for placenta previa. For example, you're more likely to have it if you:

Risk factors you can control include:

What are the symptoms?

Some women with placenta previa don't have any symptoms. But others may have warning signs such as:

  • Sudden, painless vaginal bleeding. The blood is often bright red, and the bleeding can range from light to heavy.
  • Symptoms of early labor. These include regular contractions and aches or pains in your lower back or belly.

Call your doctor if you have:

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