Placenta Accreta Spectrum Disorder

Placenta accreta spectrum (PAS) disorder is a serious pregnancy condition in which the placenta grows too deeply into the wall of the uterus. It can lead to complications during childbirth, which may necessitate a C-section or hysterectomy.

Once thought to be rare, this condition is becoming more common. Placenta accreta occurs in one of every 272 pregnancies, according to the American College of Obstetricians and Gynecologists (ACOG). This increase is likely because more people are having C-section deliveries, and the placenta is more likely to grow deeply into existing scar tissue.

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• What Is Placenta Accreta?
• What Are the Symptoms of Placenta Accreta?  
• How Do You Diagnose Placenta Accreta? 
• How Do You Treat Placenta Accreta?

What Is Placenta Accreta?

Placenta accreta spectrum disorder (PAS) is when the placenta grows too deeply into the uterine wall. It is a serious pregnancy condition – placenta accreta can be life-threatening.

The placenta is the organ that supplies oxygen and food to your growing baby through the umbilical cord. During labor, the placenta separates from your uterus right after birth. When the placenta attaches too deep, it can't easily separate. This attachment can lead to heavy bleeding and other problems. 

Thankfully, many cases of PAS are detected ahead of time using an ultrasound. If you have placenta accreta, you'll work closely with your health care team for a safe pregnancy and delivery. To stop the bleeding, your doctor may need to do a C-section or remove the uterus (a hysterectomy) after birth.

PAS encompasses three types of abnormal placental attachment:

• Placenta accreta – When the placenta attaches strongly to the uterine wall.
• Placenta increta – When the placenta attaches deeply into the uterus muscles.
• Placenta percreta – When the placenta grows through the wall of the uterus. It can even grow into nearby organs, like the bladder.

Although placenta accreta is one type of PAS disorder, the term “placenta accreta” is often used to describe any of the three types of abnormal placental attachment.

What causes placenta accreta?

One common cause of PAS is scarring from previous uterine surgery. This scar tissue is often from a previous C-section delivery. Because C-sections have become more common, so has PAS.

What are placenta accreta risk factors and complications

Placenta accreta risk factors

These factors increase your risk of placenta accreta:

• Age — People ages 35 and up have a higher risk.
• Asherman's syndrome — A condition that causes scar tissue to form in your uterus.
• Cryopreserved embryo transfer – A part of in vitro fertilization.
• Fibroid removal — This or other surgery on your uterus can leave scar tissue.
• One or more past C-sections — The risk increases with each C-section.
• Placenta previa — Your placenta sits too low and covers your cervix. Previous C-sections increase the risk of this condition as well.
• Several pregnancies — The more pregnancies you have, the higher your risk of PAS, even if you haven't had a C-section.

Placenta accreta complications

Placenta accreta is very dangerous for moms-to-be. It may cause life-threatening bleeding when you're giving birth to your baby. It might also cause you to go into labor too early.

Complications that may arise due to placenta accreta spectrum disorder include:

• Blood transfusion — Heavy bleeding might require a blood transfusion.
• Cesarean scar pregnancy — Though rare, an embryo can embed itself in a section of very thin uterine wall at the site of a C-section scar.
• Coagulopathy — A bleeding disorder in which the blood is unable to clot.
• Hysterectomy — Life-threatening bleeding may require the doctor to remove your uterus.
• Longer hospital stays — Heavy bleeding and other complications mean you'll stay in the hospital longer after delivery.
• Maternal death — PAS is life-threatening.
• Multiorgan failure — Heavy bleeding can cause other organs to fail.
• Post-traumatic stress disorder (PTSD) — The trauma of a PAS birth can cause PTSD, sexual dysfunction, or other psychological disturbances.
• Recurrence of PAS — If you have PAS once, you'll likely have it again in subsequent pregnancies.
• Sepsis — The open wound on the uterus can get infected, and this can lead to sepsis, an improper response to an infection.

PAS does not appear to affect a person’s fertility. 

Is placenta accreta life-threatening?

Placenta accreta is life-threatening. The birthing parent can bleed so heavily that they die. In an advanced medical system, it may be possible to get the rate of maternal death as low as 0.5%, according to a study in Best Practice & Research Clinical Obstetrics & Gynaecology.

However, maternal mortality from PAS depends mostly on finding it early and taking steps to avoid maternal bleeding. Historical estimates place the survival rate for expected PAS in lower-income countries around 93% — about 7% of people who are diagnosed with PAS before birth die during labor.

This number drops substantially – to a 70% survival rate — for unexpected PAS, people who don't know they have PAS before birth and labor.

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What Are the Symptoms of Placenta Accreta?  

Placenta accreta may not cause any symptoms during your pregnancy. But you might have vaginal bleeding in your third trimester.

Tell your doctor right away if you have any bleeding during your pregnancy, and go to the hospital immediately if it's severe.

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How Do You Diagnose Placenta Accreta?

It is best if your doctor finds PAS before you go into labor (antenatal). If your doctor finds PAS before birth, it is “expected PAS.” Knowing you have PAS ahead of time leads to the best outcomes, as the doctors can offer specialized care to prevent bleeding and address it if it happens.

When your doctor diagnoses PAS during delivery (intrapartum), it is “unexpected PAS.” Unexpected PAS is relatively common — risk factors like placenta previa and previous C-sections are not always present.

If your doctor thinks you're at risk for PAS, they can diagnose it with an ultrasound. Sometimes, they find it during a routine prenatal ultrasound, as well. An ultrasound is a painless test using sound waves to see your uterus.

Doctors can identify PAS on an ultrasound as early as the first trimester. However, it's most often diagnosed during the second or third trimester.

If you have placenta accreta, you'll see a maternal fetal medicine specialist. They will work with your ob-gyn to protect you and your baby during your high-risk pregnancy.

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How Do You Treat Placenta Accreta?

If you have PAS, your doctor will help you design a birth plan that's safe for you and your baby. There is no way to fix placenta accreta. Your doctor will help you make a plan to keep you and your baby as safe as possible.

They may suggest:

• Additional medical interventions — Being ready for a blood transfusion or admission to the ICU in case of severe bleeding.
• A planned C-section — The doctor will make an incision in your belly and another in your uterus to deliver your baby. There is a six-week recovery period for C-sections.
• Delivering your baby early — With expected PAS, you can carry your baby up to 36 weeks. The risk of severe bleeding and emergency C-section increases drastically after that point. Your doctor will give you medicine to ensure your baby is ready to breathe if you deliver early.
• Planned hysterectomy — Surgery to remove your uterus and prevent dangerous bleeding. Your doctor will often leave the placenta in place for a short time while they close the uterus before removing it entirely.
• Modifying your activity level — You may need to go on bed rest if you're having vaginal bleeding.

If you have PAS and you’re planning on getting pregnant again, it is crucial to talk to your doctor early to discuss treatments. A hysterectomy will leave you unable to get pregnant again, while a C-section will increase your risk of PAS in future pregnancies.

How can you prevent placenta accreta in pregnancy?

There isn't a way to prevent PAS. But you can significantly reduce your risk by only having a C-section if it's medically necessary; this will reduce scarring in your uterus. 

Make sure you tell your ob-gyn about your surgical history. If the doctor thinks you're at risk, they can do an ultrasound early to check your placenta.

By UPMC Editorial Staff. Last reviewed on 2024-09-05.