Placenta Accreta Spectrum: Accreta, Increta and Percreta

What is placenta accreta?

Placenta accreta is when part or all of the placenta attaches too firmly into the wall of the womb and does not come away after the baby is born. The RCOG describes it as "a rare but serious condition when the placenta is stuck to the muscle of your womb and/or to nearby structures such as your bladder", which "may cause heavy bleeding at the time of birth".

Clinicians now use the umbrella term placenta accreta spectrum (PAS). ACOG notes it was "formerly known as morbidly adherent placenta", and its favoured explanation is a defect in the womb lining "in the area of a uterine scar" that lets the placenta anchor abnormally deeply.

Accreta vs increta vs percreta

The three names describe how deep the attachment goes:

• Accreta – placental tissue attaches directly to the muscle of the womb, without the normal layer of lining in between.
• Increta – the tissue grows in between the fibres of the muscle.
• Percreta – the abnormal area extends through the full thickness of the womb wall, sometimes reaching the bladder.

The RCOG's 2026 guideline adds a nuance: it says what has been called percreta is better explained by a caesarean scar that has thinned and opened, with the placenta bulging through, than by placental tissue invading on its own. Hence one spectrum rather than three separate conditions.

How common is placenta accreta?

It is uncommon, but published figures vary widely, mostly because of how it is counted:

• The RCOG's patient information puts it at between 1 in 300 and 1 in 2,000 pregnancies.
• A UK national surveillance study (UKOSS, 2010–2011) found 1.7 cases per 10,000 maternities, rising to 577 per 10,000 in women with both a previous caesarean and placenta praevia.
• The RCOG's 2026 guideline cites a pooled prevalence of 1 in 817 births across 29 studies from 15 countries.
• In the US, ACOG reports a 2016 study finding 1 in 272 women with a birth-related hospital discharge diagnosis, "higher than any other published study".

The RCOG notes that loose definitions mean a placenta that was simply slow to come away often gets recorded as accreta, and estimates that between a third and a half of cases in such studies are not PAS at all.

Who is at risk?

A previous caesarean is the main risk factor, and a low-lying placenta or placenta praevia over that scar is the second. The RCOG says at least 90% of women with PAS at birth have had one or more caesareans and have a low-lying placenta or praevia. ACOG gives the risk for women with placenta praevia by which caesarean the coming birth will be:

The RCOG also links it with other surgery to the womb (such as curettage, fibroid removal or endometrial ablation), IVF and being over 35.

Placenta accreta vs placenta praevia

Placenta praevia is about where the placenta sits: covering the cervix. Accreta is about how deeply it is attached. They often occur together, and the RCOG says complications are highest when they coexist and are only discovered during birth. Most low placentas move up as the womb grows; see low-lying placenta follow-up scans.

Accreta does not add symptoms of its own that you would notice. The RCOG says that, apart from a small risk of the womb tearing, women with praevia accreta have a similar risk of bleeding and early labour in pregnancy to women with praevia alone.

How is it diagnosed?

Mainly by an expert ultrasound scan. In England, NICE's caesarean birth guideline (updated 2024) says that if your 20-week scan shows a low-lying placenta or praevia and you have a caesarean scar or a scar from other womb surgery, you should be referred for a specialist ultrasound with colour Doppler "around 28 weeks, but no later than 29 weeks". If accreta is suspected, you should be referred to a specialist placenta accreta spectrum centre.

In skilled hands, the RCOG says second-trimester ultrasound identifies over 90% of women who will have PAS at birth. On MRI the bodies differ: the RCOG does not recommend it routinely where expert ultrasound is available, while NICE says to consider it to help plan surgery.

Scans are not perfect. The RCOG's patient information says your doctor "will only be able to confirm that you have this condition at the time of your caesarean", and in the UK surveillance study only half of cases were suspected before birth.

Planning the birth at a specialist centre

If PAS is suspected, the plan is a planned caesarean in a hospital with an experienced surgical team, blood products on hand, adult intensive care and neonatal support. NICE adds that a consultant obstetrician, gynaecologist and anaesthetist should be in theatre. In the US, ACOG recommends a level III or IV maternal care centre.

• Timing. The RCOG's patient information says birth may be planned "between 35 and 37 weeks of pregnancy, depending on your individual circumstances". ACOG suggests 34+0 to 35+6 weeks.
• The placenta is not pulled away. Both colleges advise against trying to separate it, because that provokes heavy bleeding.
• Hysterectomy. ACOG calls caesarean hysterectomy, with the placenta left in place, "the most generally accepted approach". The RCOG says uterus-preserving surgery is preferable where possible, but only by expert surgeons and with your informed consent.
• Consent. The RCOG says you should understand the risks of heavy bleeding needing a blood transfusion, injury to the bladder or urinary tract, hysterectomy and intensive care, with options discussed before 34 weeks. If you would not accept blood, say so early.

When to get help urgently

If you have been told your placenta is low or accreta is suspected, the RCOG says to contact the hospital straight away if you have any vaginal bleeding, contractions or pain.

The NHS says to call 999 if you are pregnant and bleeding and you have severe tummy pain, pain in your shoulder, feel sick, faint or dizzy, or the bleeding is heavy (soaking a pad soon after putting it on).

Outlook and recovery

Planning makes a measurable difference. In the UK study, women with increta or percreta diagnosed before birth lost a median 2,750 ml of blood against 6,100 ml when it was unexpected, and fewer needed a transfusion (59% against 94%).

Deaths are rare but not zero. The RCOG reports that heavy bleeding linked to PAS was directly associated with four maternal deaths in the UK in 2019–2021.

The RCOG says you should be told about psychological support before and after the birth; our pages on birth trauma and postpartum haemorrhage cover what help exists. If your womb was kept, the RCOG says you should be told the risk of PAS happening again is high.

Frequently asked questions

What is the survival rate for placenta accreta?

Most women survive, particularly when it is found before birth. The RCOG cites a US study of 2.7 million caesarean births in which death occurred in 0.25% of births with placenta accreta spectrum, compared with 0.01% without. Planned surgery at a specialist centre is the main way that risk is reduced.

Can placenta accreta be seen on an ultrasound?

Usually, if the scan is done by an expert who is looking for it. The RCOG says skilled second-trimester ultrasound identifies over 90% of cases at birth. But it can still be missed: in the UK surveillance study, only half of cases were suspected before the birth.

Does placenta accreta always mean a hysterectomy?

No, but it often does. ACOG describes caesarean hysterectomy as the most generally accepted approach. The RCOG says surgery that keeps the womb is preferable where possible, if an expert surgeon judges it safe and you have consented after discussing the risks, including a high chance of recurrence next time.

What does placenta percreta mean?

Percreta is the most severe end of the spectrum: the abnormal area extends through the whole wall of the womb and can involve the bladder. The RCOG's 2026 guideline says this usually reflects a thinned, opened caesarean scar with the placenta bulging through, rather than the placenta invading on its own.