Placenta Accreta Spectrum
RCOG Placenta Praevia and Placenta Accreta: Diagnosis and Management (Green-top Guideline No. 27a). Last reviewed: Sep 2018.
Definition
Placenta accreta spectrum is a condition that encompasses a range of abnormal placenta attachments, ranging from abnormally adherent tissue to deeply invasive placental tissue.
Classification and Types
Depending on the invasive depth, the placenta accreat spectrum can be divided into 3 types:
| Type | Definition / description |
|---|---|
| Placenta creta (least severe) | Placental villi adhere to the uterine myometrium surface (without interposing the decidua) |
| Placenta increata | Placental villi penetrate into the uterine myometrium (reaching to the serosa) |
| Placenta percreta (most severe) | Placental villi perforate through the entire uterine wall +/- invasion of surrounding pelvic organs (most commonly the bladder) |
Aetiology
The underlying cause is linked to the trauma or disruption to the integrity of the uterine endometrium and/or superficial myometrium.
Key risk factors are those that cause scarring or damage to the uterus:
- History of placenta accreta
- Previous Caesarean section – major contributing factor
- Placenta praevia – major risk factor
- Other uterine surgery / trauma (e.g. myomectomy, endometrial curettage)
- Uterine pathologies (e.g. adenomyosis, submucousal fibroids)
Other:
- Advanced maternal age
- Assisted reproductive technologies
There is a high rate of placenta accreta spectrum and placenta praevia co-existence.
This is because placenta praevia strongly predisposes the development of placenta accreta spectrum. However, the reverse is not true (i.e. plaenta accreta spectrum does NOT predispose the development of placenta praevia).
Clinical Manifestation
Typical presentation:
- Massive haemorrhage at delivery – hallmark feature
- Often the 1st sign that a woman has placenta accreta spectrum
- This often necessitates massive blood transfusions and can rapidly cause coagulopathy, multisystem organ failure and death
- Failure of placenta separation at delivery with usual clinical measures
- If the adherent placental tissue is forcefully or manually separated, it can trigger immediate and catastrophic bleeding
Placenta percreta (the most severe form) can present with features of pelvic organ invasion
- The bladder is most commonly involved, which classically causes haematuria and storage / voiding symptoms
Antepartum haemorrhage (bleeding before delivery) is possible, but this is usually driven by the presence of a co-existing placenta praevia (common).
Isolated placenta accreta spectrum is typically asymptomatic until delivery → up to 2/3 cases remain undiagnosed until delivery
Investigation and Diagnosis
Approach (similar to placenta praevia):
- Placenta accreta spectrum is often screened via the 18-21 week TAUS
- If the TAUS raises suspicion of placenta accreata spectrum → TVUS
Definitive diagnosis: histopathological examination of the involved tissue after delivery
Management
Known Placenta Accreta (Antenatal Diagnosis)
The baby must be delivered in a specialist centre by an MDT
| Delivery timing | Planned delivery at 35 – 36+6 weeks of gestation is recommended, assuming there are no other risk factors for pre-term delivery |
| Mode of delivery | Preferred and safest: Caesarean hysterectomy, which involves:
Alternative options (specialist decision, after robust risk-benefit balancing and extensive counselling):
|
Attempts to manually separate the placenta from the uterine wall are STRONGLY ADVISED AGAINST, as this routinely triggers catastrophic, life-threatening haemorrhage and almost always results in a hysterectomy anyway.
Undiagnosed Placenta Accreta Spectrum (Identified At Delivery)
The following applies to placenta accreta spectrum that is identified DURING a routine C-section (where placenta accreta spectrum is NOT expected or NOT diagnosed).
| Scenario | Recommended management |
|---|---|
| Before delivery (i.e. the abdomen has been opened during a routine C-section and the surgeon sees the placenta accreta) | Delay the surgery:
|
| After delivery (i.e. C-section has been done and the baby has been delivered, and the placenta unexpectedly fails to separate) | Leave the placenta in situ and perform an emergency hysterectomy |
Attempts to manually separate the placenta from the uterine wall are STRONGLY ADVISED AGAINST, as this routinely triggers catastrophic, life-threatening haemorrhage and almost always results in a hysterectomy anyway.