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Placenta previa is a condition where the placenta stays in the lower part of your uterus throughout your pregnancy. When this happens, the placenta might cover all or part of your cervix — the entrance to the birth canal.
It's normal for the placenta to lie near the cervix in the early part of pregnancy. As your baby grows, it moves higher, until it is further from the cervix by the third trimester.
But sometimes the placenta will stay too low. This increases your risk of severe bleeding during labor when the cervix dilates.
Placenta previa happens in about 1 out of 200 pregnancies.
There are 2 types of placenta previa:
As you near your due date, your cervix thins and widens so your baby can pass through.
If the placenta is too close to the cervix, blood vessels attached to it can tear. Any type of placenta previa can cause a hemorrhage in your third trimester or when you're in labor.
A low-lying placenta is one that is not blocking the cervix, but is within 2 cm of the cervix opening.
The exact cause of placenta previa is unknown.
It might be due to scarring or damage to the uterine lining from surgery on the uterus.
Some women are more likely to have placenta previa, such as those who:
If you've had placenta previa in the past, there's a 4 to 8% chance you could have it again.
Placenta previa can cause life-threatening bleeding during labor.
More than likely, you'll need to have your baby by C-section.
Problems from placenta previa bleeding can include:
If you have to deliver early, placenta previa might also cause complications for your baby, such as:
While you can't prevent this condition, you and your care team can manage it by optimizing your blood count throughout your pregnancy and being prepared for extra bleeding at delivery.
It's crucial to follow your doctor's advice about ways to reduce the risk of placenta previa bleeding.
UPMC's Division of Maternal Fetal Medicine brings a team of experts together to manage high-risk pregnancies, including placenta previa.
We also provide complete care throughout all stages of your pregnancy.
The main symptom of placenta previa is bright red bleeding in the later part of your pregnancy. It might start, stop, and then start again when you're in labor.
Many women have no placenta previa symptoms, but it can be diagnosed on ultrasound.
Placenta previa bleeding is usually painless, without contractions, but you might have cramps.
If you have any bleeding during your pregnancy, it's vital to call your doctor. If your bleeding is heavy, go to the ER right away.
Placenta previa is usually diagnosed during a routine prenatal ultrasound.
If you have bleeding during your pregnancy, you may need a transvaginal ultrasound. Your doctor will place the ultrasound wand into your vagina to get a closer look at your cervix and placenta position.
Your doctor might also order:
Treatment helps prevent serious bleeding and allows you to carry your baby to term — at least 36 weeks. Your MFM care team will work with you to weigh the risk of bleeding against the risk of delivering your baby early.
Placenta previa treatments might include:
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