The placenta grew into the womb. Britain opened a national investigation.

The Health Services Safety Investigation Body (HSSIB) has opened a national inquiry into placenta accreta spectrum — a rare, life-threatening pregnancy complication in which the placenta attaches too deeply, or grows into, the wall of the womb. The investigation will look at why so many cases are still missed before birth, and why women who need specialist centres do not always get there in time.

This is not a new disease. It has become more common as caesarean births have risen, and it is a leading cause of massive obstetric haemorrhage. What changed this week is that a statutory investigator with power to compel answers is treating delayed diagnosis as a system problem.

What PAS actually is

In a typical birth the placenta peels away after the baby is born. In placenta accreta spectrum it does not. The placenta has grown into the muscle (accreta), through it (increta), or out toward other organs (percreta). Removing it can tear the uterus. Many women need a hysterectomy at the same operation that delivers the baby.

There is no single blood test that confirms PAS before birth. Diagnosis is a probability: risk factors plus ultrasound signs. Campaign group Action for Accreta has said 61 percent of the women in its research were undiagnosed until delivery.

What changed

HSSIB will look at timely diagnosis, referral to a specialist centre, and the system factors that block both. A report is expected in summer 2027. The announcement followed evidence from more than 100 families. Action for Accreta called the inquiry a landmark for NHS maternal safety and estimated £37 million a year in harm from late PAS care. Erin Cooper, a nurse from Bedfordshire who developed PAS, told the BBC the investigation will not change her outcome — but it might stop the same story happening to someone else.

That sits next to the updated RCOG Green-top Guideline No. 27a (30 June 2026). The fifth edition no longer treats PAS as something that only follows placenta praevia or a previous caesarean. It lists other uterine trauma — curettage, hysteroscopic surgery, endometrial ablation, uterine artery embolisation, myomectomy — and adds caesarean-scar ectopic pregnancy as a possible precursor. High-probability cases should have an antenatal plan with an expert multidisciplinary team and birth in a specialist centre.

Competing viewpoints

Specialist centres treat PAS as a planned team operation. Campaigners say that pathway exists on paper and fails in practice. If most cases are still a surprise in theatre, the bottleneck is who gets the extra scan and who is allowed to refer. Centralising birth for high-probability PAS saves lives and is also a longer journey for a family that wanted a local delivery.

What to watch

Risk is higher after any surgery that scars the uterus, not only a caesarean. Mention prior D&C, ablation, myomectomy, or embolisation at the first antenatal appointment. If someone uses the words “low-lying placenta” after a previous uterine scar, ask whether a specialist ultrasound has been booked. The HSSIB report will not land until summer 2027. Until then the practical standard is the June 2026 RCOG guideline. This site is not a clinic. If you are pregnant and worried about placental attachment, talk to your midwife or obstetrician.

Sources: HSSIB investigation page (21 September 2026); BBC (22 September 2026); RCOG Green-top Guideline No. 27a (30 June 2026).