What is placenta previa?

Bleeding can happen at any time during pregnancy. Placenta previa can cause bleeding late in pregnancy. This means after about 20 weeks.

When the placenta is attached close to the opening of the uterus (cervix) or covers the cervix, it is called placenta previa. There are 3 types of placenta previa:

• Complete placenta previa. The placenta completely covers the cervix.

• Partial placenta previa. The placenta is partly over the cervix.

• Marginal placenta previa. The placenta is near the edge of the cervix.

What causes placenta previa?

Researchers don't know what causes placenta previa. It is more likely to happen with certain conditions. These include:

• Past pregnancies

• Tumors (fibroids) in the uterus. These are not cancer.

• Past uterine surgeries or cesarean deliveries

• People who is older than 35

• People who is African American or of another nonwhite ethnic background

• Cigarette smoking

• Placenta previa in a past pregnancy

• Being pregnant with a boy

What are the symptoms of placenta previa?

The most common symptom of placenta previa is bright red, painless bleeding from the vagina. This is most common in the third trimester of pregnancy.

The symptoms of placenta previa may look like other health conditions. Make sure to see your healthcare provider for a diagnosis.

How is placenta previa diagnosed?

Your healthcare provider will ask about your health history. They will do a physical exam. The provider will also do an ultrasound. An ultrasound uses sound waves to make a picture of the organs. It can show where the placenta is and how much is covering the cervix. You may have a transvaginal ultrasound instead.

An ultrasound may show that a placenta is near the cervix in early pregnancy. But only a few people will develop true placenta previa. It is common for the placenta to move away from the cervix as the uterus grows.

How is placenta previa treated?

There is no treatment to change the position of the placenta. You may need:

• More ultrasounds to track where the placenta is

• Bed rest or hospital stay 

• Early delivery of the baby. This will be based on how much bleeding you have, how far along your baby is, and how healthy the baby is.

• Cesarean section delivery

• Blood transfusion for severe blood loss

What are possible complications of placenta previa?

The greatest risk of placenta previa is too much bleeding (hemorrhage). Bleeding often happens as the lower part of the uterus thins during the third trimester of pregnancy. This causes the area of the placenta over the cervix to bleed. The risk of bleeding is higher if a lot of the placenta covers the cervix. Other complications include:

• Placenta doesn't attach to the uterus as it should

• Slowed growth of your baby in the uterus

• Preterm birth (before 37 weeks of pregnancy)

• Birth defects

When should I call my healthcare provider?

Call your healthcare provider about any bleeding you have while pregnant. Bleeding during pregnancy may not be serious. If the bleeding is moderate to severe, or you have pain, contact your healthcare provider right away.

Key points about placenta previa

• Placenta previa is a cause of bleeding late in pregnancy. This is after about 20 weeks.

• It causes bleeding because the placenta is close to or covers the cervix.

• Bleeding with placenta previa is painless.

• You may need bed rest or early delivery of your baby.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

• Know the reason for your visit and what you want to happen.

• Before your visit, write down questions you want answered.

• Bring someone with you to help you ask questions and remember what your provider tells you.

• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

• Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.

• Ask if your condition can be treated in other ways.

• Know why a test or procedure is recommended and what the results could mean.

• Know what to expect if you do not take the medicine or have the test or procedure.

• If you have a follow-up appointment, write down the date, time, and purpose for that visit.

• Know how you can contact your provider if you have questions.