Placenta accreta: what it is, symptoms, risks and how birth is planned

The placenta develops alongside the baby, attaches to the wall of the womb and passes oxygen and nutrients from your blood to your baby. It is normally delivered shortly after the baby is born, which is why it is sometimes called the afterbirth.

The RCOG explains that in placenta accreta the placenta grows into the muscle of the uterus, making delivery of the placenta at the time of birth very difficult. The RCOG guideline uses the term placenta accreta spectrum to describe this group of conditions, which are associated with high rates of illness for mother and baby because of bleeding before or during birth and preterm birth.

It is often discussed alongside placenta praevia, where the placenta attaches low in the womb and may partly or completely cover the cervix. The two conditions are different, but accreta is more common in people who have placenta praevia and have had a previous caesarean.

Placenta accreta does not usually cause symptoms on its own. The RCOG says it may be suspected during the ultrasound scans you have in pregnancy, and that additional tests such as MRI may help with the diagnosis.

If there is a low-lying placenta or placenta praevia as well, bleeding can occur. The RCOG says placenta praevia may be suspected if you have bleeding in the second half of pregnancy, that the bleeding is usually painless and may occur after sex, and that it can be heavy enough to put you and your baby at risk. The RCOG advises that if you know you have a low-lying placenta you should contact the hospital straight away if you have any vaginal bleeding, contractions or pain.

The RCOG says placenta accreta is more common in women with placenta praevia who have previously had one or more caesarean births. It can also occur after other surgery to the uterus, or if you have a uterine abnormality such as fibroids or a bicornuate uterus. It is more common if you are older (over 35 years) or have had fertility treatment, especially IVF.

The RCOG guideline notes that rates of placenta praevia and accreta have increased and are likely to keep increasing because of rising rates of caesarean birth and use of assisted reproductive technology.

Placenta praevia itself is more common if you have had one or more previous caesareans, had fertility treatment or smoke.

A low-lying placenta is checked for at the routine 20-week ultrasound scan. The RCOG says 9 out of 10 women with a low-lying placenta at 20 weeks will no longer have one at the follow-up scan, but if you have previously had a caesarean the placenta is less likely to move upwards. Follow-up scans are offered at 32 weeks and, if the placenta is still low, at 36 weeks.

Placenta accreta may then be suspected on ultrasound. The RCOG says MRI scans may help, but your doctor will only be able to confirm the condition at the time of your caesarean. If it is suspected before birth, your doctor will discuss your options and the extra care that you will need at the time of birth.

There is no medicine that treats placenta accreta. The RCOG describes the planning of the birth. It may be planned for you to have your baby early, between 35 and 37 weeks, depending on your circumstances. You will need to give birth in a hospital with specialist facilities and a team with experience of caring for women with this condition.

Because of the risk of heavy bleeding, the RCOG says a hysterectomy (removal of the uterus) may be needed to stop it. Your team may discuss a planned caesarean hysterectomy, where the uterus is removed with the placenta still in place straight after the baby is born, if placenta accreta is confirmed at delivery.

It may be possible to leave the placenta in place after birth to allow it to absorb over several weeks or months. The RCOG says this approach is often not successful and can be associated with very serious complications such as bleeding and infection, and that some women still go on to need a hysterectomy. There is also a risk of injury to the bladder during delivery of the placenta.

The RCOG says if you have placenta praevia you are more likely to need a blood transfusion. Blood should be available during a planned caesarean. If you feel you could never accept a blood transfusion, tell your healthcare team as early in pregnancy as possible so that alternative plans can be discussed.

Even with no previous symptoms, the RCOG says there is a small risk that you could bleed suddenly and heavily, which may mean an emergency caesarean. If you know you have a low-lying placenta or placenta praevia, contact the hospital straight away if you have any vaginal bleeding, contractions or pain.

Call 999 if bleeding is heavy or you feel faint, and do not drive yourself. Call your maternity unit or NHS 111 for any lighter bleeding, as they will want to assess you.

Placenta accreta is identified within routine NHS maternity care: your midwife and doctor review risk factors at booking, the placental position is recorded at the 20-week scan, and follow-up scans and specialist ultrasound are arranged if needed. If it is suspected you are referred to a hospital with a team experienced in this condition and equipped to deal with heavy bleeding.

Private maternity care is available, but because of the need for blood products, intensive care and a team of specialists, ask any provider which hospital would deliver your baby and who would be in the multidisciplinary team.