Placenta Accreta: Causes, Risks and Treatment

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Placenta accreta is a rare but serious pregnancy complication where the placenta attaches too deeply into the wall of the uterus and doesn’t detach after birth. This can lead to heavy bleeding and other complications, but with early diagnosis and the right care, it can often be managed safely. You may be more at risk if you’ve had previous caesarean births, placenta praevia, are over 35, or became pregnant through fertility treatment. Continue reading and you’ll learn about the causes, risks, how placenta accreta is diagnosed, and what treatment might involve.

What Is Placenta Accreta?

Placenta accreta is a rare pregnancy complication that occurs when the placenta (the organ that forms in your uterus during pregnancy) grows into the muscle of the uterus, making it difficult to remove after birth and increasing the risk of bleeding. 

It’s more likely if you have placenta praevia but also if you have had previous caesarean births, other uterine surgery, or conditions such as fibroids. The risk also increases if you’re over 35 or have had fertility treatment, especially IVF.

If placenta accreta is suspected, you may be referred for a placenta accreta ultrasound or an MRI to confirm the diagnosis. Depending on your situation, birth may be planned early, between 35 and 36 weeks, to support a safe delivery.

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Symptoms of Placenta Accreta

Placenta accreta may not cause any noticeable symptoms during pregnancy. Often, it’s picked up during routine scans rather than through physical signs.

However, it may lead to complications around the time of birth, including:

• Excessive bleeding during or after delivery

• Placental retention (when the placenta doesn’t detach after birth)

• Damage to the uterus or nearby organs

• Anaemia caused by blood loss

• Risk of infection.

If placenta accreta is diagnosed in advance, your medical team will make a birth plan to reduce these risks and support both you and your baby.

Types of Placenta Accreta

Placenta accreta spectrum refers to a group of conditions where the placenta attaches too deeply into the wall of the uterus. There are three types:

1. Placenta accreta. The placenta attaches too firmly to the wall of the uterus.

2. Placenta increta. The placenta grows deeper into the uterine muscle.

3. Placenta percreta. The placenta penetrates through the uterus and may attach to nearby organs, such as the bladder.

Your GP may refer to these as part of the placenta accreta spectrum, depending on how deeply the placenta has grown.

Risk Factors for Placenta Accreta

Although the exact cause of placenta accreta isn’t fully understood, several factors may increase your risk:

• Previous caesarean births or other uterine surgery

• A history of placenta praevia

• Uterine abnormalities, such as fibroids or a bicornuate uterus

• Prior uterine curettage

• Pregnancy through IVF

• Being over 35 years old

• Having had one or more previous pregnancies.

These risk factors are linked to scarring or changes in the uterus, which may lead to conditions within the placenta accreta spectrum.

Placenta Accreta Diagnosis

Placenta accreta may sometimes be spotted during a routine ultrasound, but it’s only seen in around 50% of all cases. If the scan is carried out by a specialist in PAS, detection rates may rise to 80 to 90%. In certain cases, your GP may also recommend an MRI scan. This doesn’t use radiation and is safe during pregnancy.

Placenta Accreta Complications

Placenta accreta, including increta and percreta, may lead to serious pregnancy complications. These may include life-threatening bleeding, uterine rupture, the need for a peripartum hysterectomy, and, in rare cases, maternal death. 

Surgical removal of the placenta may also result in damage to nearby organs such as the bladder or ureters.

While the condition is still uncommon, placenta accreta is thought to be increasing in frequency, possibly due to higher maternal age and a greater number of births by caesarean section.

Treatment for Placenta Accreta

If you're diagnosed with placenta accreta, your health team will likely involve a planned caesarean birth at a hospital with experience managing this condition. You may be referred to a specialist centre where your team could include obstetricians, anaesthetists and other experts.

Treatment options may include:

• Planned delivery between 35 and 36 weeks of pregnancy to lower the risk of complications

• Careful monitoring after birth for signs of infection or bleeding

• Blood transfusions before, during or after delivery if needed

• A hysterectomy if the placenta cannot be safely removed or if heavy bleeding occurs

• Interventional radiology (such as embolisation) to help control bleeding

• In some cases, the placenta may be left in place to absorb over time, though this carries risks such as infection and bleeding.

Each case is different, and your obstetric team will guide you through the safest approach for both you and your baby.

The Bottom Line

Placenta accreta can be a serious pregnancy complication, but with early diagnosis and the right care team, many of the risks may be managed. If you have any concerns during your pregnancy – especially if you notice vaginal bleeding – contact your midwife or GP without delay.

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