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Placenta Previa

Medically reviewed by Last updated on Jul 4, 2022.

What is placenta previa?

Placenta previa is a condition in which your placenta grows near or over your cervix (opening of your uterus). The placenta forms during pregnancy and provides oxygen and nutrition to your unborn baby. The placenta also removes waste products from the fetus. Normally, your placenta grows in the upper part of your uterus. When your placenta grows near your cervix, it may block the opening to your vagina. You may have vaginal bleeding that could harm you and your unborn baby.

What increases my risk for placenta previa?

The exact cause of placenta previa is not clear. Your risk increases as you get older. Your risk also increases if you are of Asian descent. The following may also increase your risk:

  • Previous placenta previa: Your risk for placenta previa increases if you have had it during previous pregnancies.
  • Infertility treatments: Treatments used to increase your ability to get pregnant may make you more likely to have placenta previa.
  • Pregnancy: The more times you have been pregnant, the higher your risk for this condition. Your risk increases if your pregnancies are less than 1 year apart. Being pregnant with more than 1 baby, such as twins, also increases your risk. Past pregnancies that resulted in an abortion or miscarriage may also increase your risk for placenta previa.
  • Past C-section: A C-section can cause changes in your uterine tissue that increase your risk for placenta previa.
  • Smoking and street drug use: Smoking before and during pregnancy increases your risk for placenta previa. Use of street drugs such as cocaine also may lead to placenta previa.
  • Uterine scarring: Placenta previa is more likely to occur if you have scarring in your uterus. Scarring may occur from a past surgery or pregnancy. Scarring may increase the risk that your placenta will grow in the lower part of your uterus.

What are the signs and symptoms of placenta previa?

  • Vaginal bleeding: Bleeding usually occurs in the late second or early third trimester of pregnancy, but can occur at any time. You may have small or large amounts of bleeding that normally does not cause pain. You may have bleeding after sex. Bleeding may also occur suddenly.
  • Contractions: Contractions may cause abdominal pain or cramping.

How is placenta previa diagnosed?

Placenta previa is often found during a normal pregnancy visit with your healthcare provider. The later in your pregnancy it is found, the higher the risk that it will not go away. Your healthcare provider will ask about your health and any previous pregnancies. Tell him or her if you have had past uterine surgeries or procedures. Your healthcare provider may check your cervix by gently putting a speculum into your vagina. A speculum is a tool that opens your vagina to help your healthcare provider see your cervix. You may also need any of the following:

  • Ultrasound:
    • Transvaginal ultrasound: A small tube is placed inside your vagina so your healthcare provider can see your uterus. It may show if your placenta lies in the lower part of your uterus. It may also show how close your placenta is to the edge or top of your cervix.
    • Abdominal ultrasound: A small device will be moved around your abdomen to show pictures of your uterus. Your healthcare provider may want you to have a full bladder for this test. It may show if your placenta is blocking the opening of your uterus. It may also show problems with your baby, such as slow growth.
      Pregnancy Ultrasound
    • Doppler ultrasound: A Doppler ultrasound may be done to check if your placenta has grown into the wall of your uterus.
  • MRI: This scan uses powerful magnets and a computer to take pictures of your pelvis. MRI pictures may show where your placenta is in your uterus. An MRI may also show if and how deep your placenta has grown into your uterine wall. You may be given dye to help the placenta show up better in the pictures. Tell the healthcare provider if you have ever had an allergic reaction to contrast dye. Do not enter the MRI room with anything made of metal. Metal can cause serious injury. Tell the healthcare provider if you have any metal in or on your body.

How is placenta previa treated?

Placenta previa may go away later in your pregnancy, and you may not need treatment. Your placenta may move when your uterus changes shape as you get closer to delivery. If you need treatment, it may depend on how far along you are in your pregnancy. Your treatment also depends on how much of your cervix is covered by your placenta. You may need any of the following:

  • Bed rest: You may need to be on bedrest until your baby is ready to be born. You may be able to rest at home, or you may need to stay in the hospital. If you are in the hospital, your healthcare provider may keep you on a monitor. A monitor is used to watch your vital signs (heart rate, breathing, and blood pressure). You may also need to wear a fetal monitor. Ask your healthcare provider which activities you may do while you are on bedrest.
  • Blood transfusion: You may need a blood transfusion if you lose a large amount of blood. During a blood transfusion, you will get donated blood through an IV. You may need a transfusion while you are still pregnant or after your baby is born.
  • Medicines:
    • Steroids: Steroids may be given if you need to deliver your baby earlier than expected. These medicines help your baby's lungs to mature and prevent breathing problems after he or she is born.
    • Rh immune globulin shot: You may be given an Rh immune globulin injection (RhIG) before your baby is born. RhIG is needed if you and your baby have different Rh blood types (incompatibility). Rh incompatibility means that your baby has a protein in his or her blood that you do not. Your body may make antibodies against your baby's blood and destroy his or her blood cells. RhIG injections prevent this from happening.
    • Tocolytics are given to stop contractions if your baby is not ready to be born.
  • Amniocentesis: An amniocentesis test may be done between weeks 36 and 37 of your pregnancy if you are not bleeding. This test is done to check your unborn baby's lungs if you have a C-section date planned. Ask your healthcare provider for more information about amniocentesis.
  • Delivery of your baby: Early delivery of your baby may be needed. If your due date is close and your placenta does not cover your cervix, you may be able to give birth vaginally. If your placenta covers most or all of your cervix, a C-section will be done. A C-section may also be done if you have heavy bleeding or you or your baby is in danger.

Treatment options

The following list of medications are in some way related to or used in the treatment of this condition.

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What are the risks of placenta previa?

  • Medicines used to treat placenta previa may cause you to have a fast heartbeat. You may be at risk for blood clots. Your placenta may pull away from your uterus when you have contractions. You may have sudden, large amounts of bleeding. You may need a blood transfusion to replace the blood you have lost. Large amounts of blood loss may be life-threatening. Placenta previa increases your risk of placenta accreta. Placenta accreta is when your placenta attaches deep into the wall of your uterus. The deep attachment makes it hard for your placenta to come out after your baby is born. Placenta accreta increases your risk for bleeding even further.
  • Your baby may not grow as he or she should inside your uterus. He or she may be forced into an abnormal birthing position. Your unborn baby may also have problems with his or her heartbeat. Your baby may be born too early and his or her lungs may not be fully developed. He or she may also be very small. This could be life-threatening for your baby. If you need surgery to deliver your baby, you may get an infection or bleed more than expected. After you give birth, you may need surgery to remove your uterus if you have bleeding that cannot be stopped. You may get a blood clot in your leg or arm. The clot may travel to your heart or brain and cause life-threatening problems, such as a heart attack or stroke.

How can I manage placenta previa?

  • Have a safety plan and someone to take you to the hospital if needed.
  • Stay within a short distance to the hospital so you can get there quickly.
  • Do not douche or have sex. These may cause bleeding.

When should I contact my healthcare provider?

  • You feel abdominal cramps, pressure, or tightening.
  • Your heart is beating faster than normal for you.
  • You have questions or concerns about your condition or care.

When should I seek immediate care or call 911?

  • You have any amount of bleeding from your vagina.
  • You are having severe abdominal pain or contractions.
  • You feel faint or too weak to stand up.
  • You suddenly feel lightheaded and short of breath.
  • You have chest pain when you take a deep breath or cough.
  • You cough up blood.

Care Agreement

You have the right to help plan your care. Learn about your health condition and how it may be treated. Discuss treatment options with your healthcare providers to decide what care you want to receive. You always have the right to refuse treatment. The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

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