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Placenta Previa

Condition Basics

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.

Normally, the placenta is attached high up in the uterus, away from the cervix. In placenta previa, the placenta forms low in the uterus and covers all or part of the cervix.

Placenta previa can cause problems such as these:

  • You may have too much bleeding, which can be dangerous for both you and your baby.
  • The placenta may separate too early from the wall of the uterus. This is called placental abruption, and it can cause serious bleeding, too.
  • The baby may be born too early (premature), at a low birth weight.

What causes it?

Healthcare providers 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:

  • Have had a surgery that affected your uterus, such as a D&C or surgery to remove uterine fibroids (myomectomy).
  • Are pregnant with twins or more.
  • Have had a previous C-section (caesarean delivery).
  • Have had 3 or more pregnancies.
  • Are age 35 or older.
  • Have had placenta previa before.
  • Have a health condition such as diabetes or high blood pressure.
  • Have had in vitro fertilization for this pregnancy.

Risk factors you can control include:

  • Smoking during pregnancy.
  • Using cocaine during pregnancy.

What are the symptoms?

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

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

How is it diagnosed?

Most cases of placenta previa are found during the second trimester during a routine ultrasound. Or it may be found when a person has vaginal bleeding during pregnancy and gets an ultrasound to find out what is causing it. Some people don't find out that they have placenta previa until they have bleeding at the start of labour.

How is placenta previa treated?

The kind of treatment you will have depends on:

  • Whether or how much you are bleeding.
  • How the problem is affecting your health and your baby's health.
  • How close you are to your due date.

If your healthcare provider or midwife finds out before your 20th week of pregnancy that your placenta is low in your uterus, chances are very good that it will get better on its own. The position of the placenta can change as the uterus grows. So by the end of the pregnancy, the placenta may no longer block the cervix.

If you aren't bleeding, you may not need to be in the hospital. But you will need to be very careful.

  • Follow your healthcare provider’s instructions about doing your routine activity or light exercise.
  • Ask your healthcare provider if you can have sexual intercourse. It’s commonly recommended that if you have placenta previa not to have intercourse after 28 weeks of pregnancy.
  • Do not put anything, such as tampons or douches, into your vagina. Use pads if you are bleeding, and call your healthcare provider or nurse call line.
  • Call your healthcare provider or midwife and go to the emergency room right away if you have any vaginal bleeding.

If you are bleeding, you may have to stay in the hospital. If you are close to your due date, your baby will be delivered. Healthcare providers always do a C-section when there is a placenta previa at the time of delivery. A vaginal delivery could disturb the placenta and cause severe bleeding.

If your bleeding can be slowed or stopped, your healthcare provider or midwife may delay delivery and monitor you and your baby closely. They may do fetal heart monitoring to check your baby's condition.

You may be given:

  • A blood transfusion if you've lost a lot of blood.
  • Steroid medicines if you aren't close to your due date. These medicines help get your baby ready for birth by speeding up lung development.
  • Tocolytic medicine to slow or stop contractions if you are in preterm labour.


Adaptation Date: 11/27/2023

Adapted By: Alberta Health Services

Adaptation Reviewed By: Alberta Health Services

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