Placenta Previa

Overview

What is placenta previa?

Placenta previa is a condition when the placenta blocks all or part of your cervix in the last months of pregnancy. The placenta develops in your uterus during pregnancy. It’s a sac-like organ that supplies oxygen and nutrients to the fetus through the umbilical cord.

The placenta stretches and grows through pregnancy. It’s common for it to be low in your uterus in early pregnancy. In the third trimester (weeks 28 to 40 of pregnancy), the placenta should move to the top of your uterus. This happens so your baby has a clear path to the vagina for delivery. Placenta previa occurs when the placenta doesn’t move to the top of your uterus. This means the placenta is blocking your baby’s exit from your vagina.

What are the types of placenta previa?

There are several types of placenta previa:

  • Marginal placenta previa: The placenta is positioned at the edge of your cervix. It’s touching your cervix, but not covering it. This type of placenta previa is more likely to resolve on its own before your baby’s due date.
  • Partial placenta previa: The placenta partially covers your cervix.
  • Complete or total placenta previa: The placenta is completely covering your cervix, blocking your vagina. This type of placenta previa is less likely to correct itself.

Each type of placenta previa can cause vaginal bleeding during pregnancy and labor. Due to the high risk of bleeding, most people will require a Caesarean (C-section) delivery.

How common is placenta previa?

Placenta previa occurs in about 1 in 200 pregnancies. Pregnancy care providers usually diagnose it in the second trimester during an ultrasound.

What is the difference between placenta previa and placental abruption?

In placenta previa, the placenta is covering all or part of your cervix. Even though the placenta is in a complicated position, it’s still attached to your uterus. A placental abruption is when the placenta detaches from your uterus. Both conditions can cause vaginal bleeding during pregnancy and labor.

Is placenta previa the same as anterior placenta?

Placenta previa isn’t the same as anterior placenta. Your placenta can grow anywhere in your uterus. An anterior placement of the placenta means the placenta has implanted in the front of your body. Think of anterior placenta as a pillow between your baby and your stomach.

Symptoms and Causes

What are the symptoms of placenta previa?

The most common symptoms of placenta previa are:

  • Bright red bleeding from your vagina. The bleeding often starts near the second half of pregnancy. It can also start, stop, then start again a few days later.
  • Mild cramping or contractions in your abdomen, belly or back.

The amount of vaginal bleeding can vary and is often not accompanied by any pain.

What causes placenta previa?

There isn’t a known cause of placenta previa. There are some factors that can increase your risk of developing placenta previa, including your medical history and certain lifestyle habits.

What are the risk factors for developing placenta previa?

There are several factors that increase your risk for placenta previa during pregnancy:

What are possible complications of placenta previa?

If you have placenta previa, there are risks for both you and your baby. Complications from placenta previa include:

For you:

  • Bleeding: Severe bleeding can occur during pregnancy, labor or delivery.
  • Early birth: If you’re bleeding severely, your healthcare provider may perform an emergency C-section before your baby is full term (40 weeks).
  • Blood loss: Anemia, low blood pressure, pale skin or shortness of breath are all side effects of losing too much blood.
  • Placenta accreta: The placenta grows too deeply in the wall of your uterus. This can cause severe bleeding after delivery.
  • Placental abruption: The placenta separates from your uterus before your baby is born. This decreases your baby’s supply of oxygen and nutrients.

For baby:

  • Premature birth: If your bleeding is severe and you need an emergency C-section, your baby may be born too early.
  • Low birth weight: Trouble staying warm and poor weight gain are potential side effects of low birth weight.
  • Respiratory issues: Underdeveloped lungs could make breathing more difficult.

Can you have placenta previa without bleeding?

Yes, it’s possible to have placenta previa and not experience vaginal bleeding. You could have mild cramping or pain in your pelvic region or back. It’s best to discuss any bleeding or pelvic pain you have with your healthcare provider.

Why do you bleed when you have placenta previa?

There are two main reasons you bleed if you have placenta previa. They have to do with how your body prepares for labor.

  • Your cervix is the opening from uterus to your vagina. As pregnancy progresses in the third trimester, your cervix thins (effaces) and spreads to prepare for birth. If your placenta is touching or covering your cervix, this thinning will cause you to bleed.
  • During labor, your cervix opens (dilates) in order to allow the baby to exit your uterus and descend down your vagina. When your cervix opens, the blood vessels connecting the placenta to your uterus are torn and can cause bleeding.

Can placenta previa cause a miscarriage?

Miscarriage occurs when you experience a loss of pregnancy before 20 weeks. Pregnancy care providers don’t typically diagnose placenta previa until around or after the 20th week of pregnancy. It’s uncommon that placenta previa would be the cause of a miscarriage.

Diagnosis and Tests

How is placenta previa diagnosed?

Pregnancy care providers usually identify placenta previa in a routine ultrasound around 20 weeks of pregnancy. It’s sometimes found when a person experiences symptoms of placenta previa like vaginal bleeding. Your provider will recommend ultrasounds to monitor the placement of the placenta for the remainder of your pregnancy.

What tests are used to diagnose placenta previa?

Your healthcare provider will diagnose placenta previa using ultrasounds that show the inside of the female reproductive system:

  • Vaginal ultrasound (or transvaginal ultrasound): Your provider places a wand-like device (a transducer) into your vagina to check the position of your baby, the placenta and your cervix.
  • Abdominal ultrasound: Your provider places gel on your abdomen, then moves a handheld device (the transducer) around the outside of your belly. This can also show the position of your baby, the placenta and your cervix.

Both types of ultrasound show the images on a monitor or screen. Your pregnancy care provider will determine how much of your cervix is covered by the placenta and recommend treatment.

Management and Treatment

How is placenta previa treated?

The goal is to get you as close to your due date as possible. Delivering via C-section is often the safest treatment if bleeding continues. Treatment of placenta previa depends on:

  • How severely you’re bleeding.
  • The gestational age of your baby.
  • The position of the placenta and your baby.
  • The health of you and your baby.

If your provider finds placenta previa early in your second trimester, it can get better on its own. The position of the placenta can change as your uterus expands to accommodate the growing baby. There is often less of a chance that the placenta will move higher in your uterus if your provider diagnoses you with the condition later in pregnancy.

If the placenta is near or covering just part of the cervix and you’re not bleeding, your healthcare provider may recommend:

  • Reducing strenuous activities like running, lifting and exercising.
  • Bed rest at home.
  • No sexual intercourse, tampons or douching.
  • More frequent prenatal appointments and ultrasounds.

For moderate to severe cases of placenta previa or frequent bleeding, other treatments could include:

  • Bed rest in the hospital.
  • Medicine to prevent early labor.
  • Steroid shots to help the baby's lungs develop faster.
  • Blood transfusions if you experience heavy bleeding.
  • An emergency C-section for heavy, uncontrolled bleeding.

Does placenta previa go away?

Placenta previa can go away on its own if it’s found in the second trimester. Going away on its own means the placenta shifts upwards to the top of your uterus. As your uterus expands in the third trimester, the placenta may still move. The later in the pregnancy it remains covering the cervix, the less likely it is to go away. Your healthcare provider will monitor the position of the placenta to see if the condition has resolved before delivery.

Prevention

Can I reduce my risk for placenta previa?

There is nothing you can do to prevent placenta previa and no surgical or medical procedure can correct it. There are certain risk factors for placenta previa that are within your control, like not smoking or using cocaine. Once your provider diagnoses the condition, there are ways to reduce the amount of vaginal bleeding.

Outlook / Prognosis

What can I expect if I have placenta previa?

Your treatment will be unique to your condition. Most people can expect:

  • Frequent monitoring through the second and third trimester. Your provider does this to check the position of the placenta and watch for any changes in symptoms.
  • Modified or restricted physical activities like exercise and sex.
  • Blood tests post-delivery to check your blood counts.

Will my baby be born early if I have placenta previa?

Maybe. Your healthcare provider will consider the amount of bleeding, the position of the placenta and the baby’s gestational age before deciding if an early delivery is necessary. Around 36 weeks of pregnancy, the best option for the health of you and your baby could be an early delivery. Other times a person reaches full term or 40 weeks of pregnancy.

Can I still have a vaginal delivery with placenta previa?

If you have a marginal placenta previa (the placenta is close to your cervix, but not covering it), your healthcare provider may be able to deliver your baby vaginally. This carries a risk of bleeding and may be too dangerous. Your provider will discuss the safest way to deliver your baby.

Will I need a C-section if I’m diagnosed with placenta previa?

A C-section is usually the safest delivery option if you have placenta previa. If the placenta covers even a part of your cervix, a vaginal delivery can cause severe bleeding. Your provider will typically schedule your C-section in advance, but if your bleeding is too severe at any time, you may need an emergency C-section.

Can placenta previa cause birth defects?

It’s uncommon for placenta previa to cause birth defects. Your baby may be born premature if your healthcare provider feels it’s the safest time to deliver. Premature birth carries some complications such as low birth weight and respiratory problems.

Will I get placenta previa again?

If you’ve had placenta previa in a past pregnancy, your chances of having it again are around 2%. If you become pregnant, let your healthcare provider know so that they’re aware of your medical history.

Will placenta previa affect my fertility?

Placenta previa doesn’t impact your chances of getting pregnant again. You’ll have a small risk of getting placenta previa again if you become pregnant.

What questions should I ask my doctor?

Your healthcare provider should be able to answer your questions and prepare you for treatment of placenta previa. Here are some questions you might ask:

  • Is the baby’s life in danger? Is mine?
  • What are my treatment options?
  • How will I know if my placenta previa goes away?
  • Should I limit certain activities?
  • Can the baby be born now?
  • What are potential complications?
  • Will I need additional ultrasounds or tests?
  • What are the signs that I need to go to the hospital?

What questions will my doctor ask me?

  • When did you first notice bleeding?
  • How heavy is the bleeding?
  • Is bleeding constant or does it come and go?
  • Do you have any pelvic pain?
  • Have you had pregnancy complications before?
  • Have you had uterine surgeries?
  • Do you smoke or use cocaine?
  • Is there someone to care for you if bed rest is required?

Living With

When should I see my healthcare provider?

Call your healthcare provider immediately if you’re bleeding, cramping or experiencing pelvic pain during your pregnancy, especially in the second half of pregnancy.

When should I go to the ER?

If you’re experiencing severe blood loss, you should seek emergency medical care immediately. Major blood loss carries several serious side effects to both you and your baby.

Can I exercise with placenta previa?

Your healthcare provider will likely advise you to limit certain activities like exercise, squatting, jumping and lifting. These activities could cause bleeding. It's best to discuss your day-to-day activities with your provider so they can suggest modifications as necessary.

Can I have sex if I have placenta previa?

Most healthcare providers will advise against having sexual intercourse if you have placenta previa. It’s best to avoid any activities that can trigger bleeding or contractions, like using tampons, douching or inserting anything into your vagina.

A note from Cleveland Clinic:

Placenta previa is a treatable condition where most people go on to deliver healthy babies. You’re likely to have a safe delivery if you follow the guidance of your pregnancy care provider. Don’t be afraid to speak up if you experience any bleeding or discomfort during your pregnancy.

Last reviewed by a Cleveland Clinic medical professional on 09/26/2022.

References

  • American College of Obstetricians and Gynecologists. Bleeding during pregnancy. (https://www.acog.org/patient-resources/faqs/pregnancy/bleeding-during-pregnancy) Accessed 9/26/2022.
  • American Journal of Obstetrics & Gynecology. Society for Maternal-Fetal Medicine (SMFM) Consult Series #44: Management of bleeding in the late preterm period. (https://www.ajog.org/article/S0002-9378(17%2931212-7/pdf) Accessed 9/26/2022.
  • American Pregnancy Association. Placenta Previa: Symptoms, Causes and Treatment. (http://americanpregnancy.org/pregnancy-complications/placenta-previa/) Accessed 9/26/2022.
  • March of Dimes. Placenta previa. (https://www.marchofdimes.org/complications/placenta-previa.aspx) Accessed 9/26/2022.
  • Merck Manual. Vasa Previa. (https://www.merckmanuals.com/home/women-s-health-issues/complications-of-pregnancy/vasa-previa) Accessed 9/26/2022.
  • Silver RM. Abnormal Placentation: Placenta Previa, Vasa Previa, and Placenta Accreta. (https://pubmed.ncbi.nlm.nih.gov/26244528/) Obstet Gynecol. 2015 Sep;126(3):654-668. Accessed 9/26/2022.

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