Placenta accreta: risks and treatment

Placenta accreta is a condition where the placenta (afterbirth) attaches very deeply to the muscle of the uterus. After childbirth, the placenta may not separate from the uterus, sometimes causing torrential bleeding.

Placenta accreta is an uncommon condition, but with the possibility of serious complications.

It has been on the rise for the past 60-70 years and we see it more often now. It is more common in women who have had a caesarean section.

The rise in caesarean sections has propelled a rise in cases of placenta accreta.

1 in 4027 pregnancies in the 1970s had placenta accreta, rising to 1 in 2510 pregnancies in the 1980s and 1 in 533 at present.

What is placenta accreta?

Also called morbidly adherent placenta, the placenta invades deeply into the muscle wall of the uterus.

There is a protective layer called the decidua basalis in the wall of the uterus which protects the wall of the womb from being attached too deeply to the placenta.

Damage to this decidua basalis is thought to predispose to a morbidly adherent placenta.

Risk factors for placenta accreta

Damage to the decidua basalis can occur in many conditions like a previous caesarean section or uterine surgery.

Risk factors for placenta accreta are:

  • Caesarean section – If you have had a previous caesarean section, you are at risk of placenta accreta.
3 in 1000 women with a previous caesarean section develop placenta accreta. The risk increases with every caesarean section. With 5 or more caesarean sections the risk is 60 in 1000.

  • Placenta Praevia – Low lying placenta increases the risk of placenta accreta.
4-5 in 100 women with low-lying placenta have a morbidly adherent placenta.

If in addition to a low-lying placenta, you have had a caesarean section, your risk increases to 10-24 in 100.

With 2 previous caesarean sections, this risk is increased further. 3-5 in 10 women will have placenta accreta.

  • Fibroids of the uterus – You have a higher risk of placenta accreta if you have fibroids. This is only so if the placenta attaches to the area of the fibroid. Small fibroids less than 3 cm generally do not pose a risk.
If you have had surgery to remove the fibroids of the womb in the past, it increases your risk of having a morbidly adherent placenta.

  • Age – If you are over the age of 35 you are at higher risk of a morbidly adherent placenta.
  • Fertility treatment – Women who have had fertility treatment like IVF and get pregnant are at higher risk of placenta accreta.

Spectrum of placenta accreta

Are all cases of morbidly adherent placenta the same?

No, they are not.

They can range in severity depending on how deeply they invade the wall of the uterus.

There are 3 types:

  • Placenta accreta
  • Placenta increta
  • Placenta percreta
Placenta accreta is only superficial attachment, but deeper than in a normal pregnancy.

Placenta increta invades more deeply.

Placenta percreta invades the entire thickness of the wall of the womb and may also invade the urinary bladder.

Placenta percreta is associated with the most serious complications.

Risks of placenta accreta

The risks of placenta accreta are:

  • Bleeding – The commonest risk is bleeding after childbirth. The birth of the baby is not followed by the placenta. Sometimes, it may separate but with very heavy bleeding.
If you are having a caesarean section, the placenta may be difficult to separate. Many times it may be first detected at the time of operation. The placenta will be difficult to remove and there is usually more bleeding than normal.

  • Infection – Parts of the placenta may be left attached to the womb and this may cause infection of the womb, requiring antibiotics.
  • Hysterectomy – a small number of women will need the womb to be removed because the placenta is so deeply attached and is impossible to remove. Careful planning and discussion during pregnancy is the norm . You will be informed of the risks, options and the opportunity to discuss your concerns with your Obstetrician, Anaesthetist and midwife.
  • Extensive surgery – If the placenta invades through the urinary bladder or the tubes connecting the kidney to the bladder (ureter), this may require surgery to fix this and a surgeon specialist may be present at the time of the operation.
  • Recurrence – 2 in 10 women who have placenta accreta will have it agian in a future pregnancy.

Diagnosis of placenta accreta

Suspicion of placenta accreta would lead your Obstetrician to request an ultrasound scan to especially look for features of placenta accreta.

After an ultrasound scan that suggests morbidly adherent placenta, your specialist would sometimes ask for an MRI scan. An MRI scan gives more information about how deeply the placenta has invaded, especially if the placenta is attached to the back wall of the uterus. It would also show if it is close to the bladder and ureter.

All cases of placenta praevia and previous caesarean section with placenta lying near the scar would have a scan to look for placenta accreta. Most cases would be referred to a specialized centre with expertise in dealing with placenta accreta.

Can placenta accreta happen without these risk factors?

Could it be missed on scan?

The answers to both these questions are yes.

Is there any other test that can give a clue to the condition?

Some blood tests like raised serum alpha-fetoprotein have been seen in cases of placenta accreta. However, they are not seen consistently with placenta accreta and can’t be used to detect this condition.

A promising new test?

An exciting new study was published in Nature Communications on the 3rd of August 2021.

Scientists used nanotechnology by using NanoVelcro Chips to detect placental cells called trophoblasts in mum’s blood.

A simple blood test done in the first 3 months of pregnancy could possibly detect placenta accreta. Clusters of trophoblasts suggest placenta accreta.

The researchers are refining the test to make it more reliable and accurate.

This could potentially detect cases early helping doctors plan and tailor treatment for this potentially dangerous condition.

Treatment of placenta accreta

Once detected, you will be referred to a higher centre with expertise in the management of this condition.

The option of removal of the womb after delivery of the baby will be discussed.

For women who wish to conserve the uterus, you will be informed about the options.

There is normally a lot of blood loss during surgery and blood transfusion and its risks will be discussed.

Even if women wish to conserve the uterus it may not be possible at times.

Sometimes, Obstetricians may leave the placenta in the uterus as separating it can cause a lot of blood loss.

This can cause infection and blood loss later and generally speaking this is not the way forward in most cases.

Women who do not have a hysterectomy are at higher risk of placenta accreta in a subsequent pregnancy (2 in 10). This itself may deter them from conceiving again.

Caesarean section: the biggest culprit?

There has been a trend in women to go in for a planned caesarean section for no reason at all, simply convenience!

There was a time when Obstetricians would talk you out of it.

Now, most doctors oblige possibly fearing litigation in case something went wrong at normal delivery.

Each and every delivery can turn high risk from low risk, and only Allah swt knows the outcome.

But, normal delivery is so called for a reason.

Caesaean should be used as and when needed as decided by your doctor.

Although only a small number of women will develop placenta accreta following caesarean section, it is dangerous and life-threatening.

Take home message

Choose to have a normal delivery.

If caesarean has to be done it is best not to have more than 2 as risk of placenta accreta goes on increasing with every caesarean section.