Placenta accreta spectrum !

In placenta accreta the placenta grows too deeply into the uterine wall and does not separate after birth, causing life-threatening bleeding.

Updated 2026-11-01

Structures involved

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Why it happens

What it is

Abnormal, deep attachment of the placenta to the uterine wall because the normal decidual layer is missing. The placenta cannot separate after the baby is born, and attempts to remove it cause massive haemorrhage. It includes accreta (attached to the myometrium), increta (invading into the myometrium) and percreta (through the uterine wall, sometimes into the bladder or other organs).

Who gets it

Its frequency has risen sharply in parallel with caesarean section rates and now affects roughly 1 in 300 to 1 in 1,000 deliveries in many countries. Latin America, including Colombia, has some of the highest caesarean rates in the world, which makes this condition increasingly relevant. It is a leading cause of emergency peripartum hysterectomy.

Causes

Defective decidua at the implantation site, mostly over a previous uterine scar
Trophoblast invades beyond its normal limit into the myometrium

Risk factors

Placenta previa with one or more previous caesarean sections (the strongest risk factor; risk rises with each caesarean)
Previous uterine surgery: myomectomy, curettage, endometrial ablation
Caesarean scar pregnancy
Asherman syndrome (intrauterine adhesions)
Advanced maternal age and multiparity
Pregnancy after in vitro fertilisation

Pathophysiology

Where the endometrium has been damaged, usually by a caesarean scar, the decidua basalis and its natural cleavage plane (the Nitabuch layer) are absent. Chorionic villi attach directly to, invade or penetrate the myometrium, together with abnormally large and numerous vessels. At delivery the placenta does not separate and the uterus cannot contract around the attachment site, so bleeding is torrential.

Classification

Placenta accreta (creta): villi attach to the myometrium without invading it (most common)
Placenta increta: villi invade into the myometrium
Placenta percreta: villi pass through the serosa and may invade the bladder or other pelvic organs
FIGO clinical grading 1–3 at delivery

Symptoms and signs

Often no symptoms during pregnancy; found on screening ultrasound
Painless vaginal bleeding when associated with placenta previa
Haematuria when the placenta invades the bladder (percreta)
At delivery: placenta fails to separate, followed by massive bleeding when removal is attempted

Diagnosis

Clinical: Suspected in every woman with placenta previa or a low anterior placenta over a caesarean scar. Confirmed at surgery and by histology; clinical findings at delivery (no separation, invasion) define the grade.
Tests: Complete blood count, blood group and cross-match, coagulation tests and fibrinogen in preparation for massive transfusion. There is no reliable blood test for diagnosis.
Imaging: Ultrasound with colour Doppler is the main tool: loss of the clear zone behind the placenta, multiple placental lacunae, thinning of the myometrium, bladder wall interruption and abnormal vascularity. MRI helps define depth, lateral extension and posterior placentas.

Differential diagnosis

Placenta previa without invasion
Retained placenta from other causes (trapped placenta, uterine atony)
Placental abruption
Uterine rupture
Uterine fibroids distorting the placental site

Goal of treatment

Detect the condition before delivery and plan a scheduled birth by an experienced multidisciplinary team in a well-resourced centre to limit blood loss and protect the mother’s life.

Treatment

Procedure: Planned delivery, usually by caesarean section around 34–35 weeks, before labour starts, in a referral centre with blood bank, intensive care and surgical specialists (obstetrics, urology, vascular or interventional radiology).
Surgical: Caesarean hysterectomy with the placenta left in place is the standard treatment; uterine-sparing (conservative) management is considered only in selected cases with experienced teams.
Medical: Massive transfusion protocol with balanced blood products, tranexamic acid for bleeding, and correction of fibrinogen and calcium.
Procedure: Ureteral stents, aortic or internal iliac balloon occlusion and uterine artery embolisation may be used to reduce bleeding in selected cases.
Follow-up: Nursing priorities: large-bore intravenous access, cross-matched blood available, measured blood loss, vital signs, urine output and haematuria, temperature and coagulation; post-operative intensive care monitoring.

Complications

Massive obstetric haemorrhage and hypovolaemic shock
Disseminated intravascular coagulation
Loss of fertility from hysterectomy
Bladder and ureteral injury
Infection, venous thromboembolism and intensive care admission
Preterm birth from planned early delivery, and maternal death

Prognosis

With antenatal diagnosis and a planned multidisciplinary delivery, maternal outcomes are much better than with unexpected diagnosis at birth. Maternal mortality remains significant where it is discovered unexpectedly or in centres without blood and intensive care. Neonatal outcome depends mainly on gestational age.

Prevention

Avoiding caesarean sections without a medical indication
Ultrasound review of the placental site in women with previous uterine surgery, especially with placenta previa
Early referral to a specialist centre when the condition is suspected

Test yourself

Think of the answer, then tap the question to see it.

What is the strongest risk factor for placenta accreta spectrum?

Placenta previa in a woman with one or more previous caesarean sections.

How do accreta, increta and percreta differ?

By depth: attached to the myometrium, invading into it, or passing through the serosa (possibly into the bladder).

What is the standard management?

Planned caesarean hysterectomy with the placenta left in place, by a multidisciplinary team.

What is the main imaging test?

Ultrasound with colour Doppler, with MRI as a complement.

What should be avoided if the placenta does not separate after birth?

Forcible manual removal or traction, which can provoke massive haemorrhage.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: Placental Accreta, Increta and Percreta (March of Dimes, 2024); Maternal mortality (World Health Organization, 2025).

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Representative model, for educational purposes only.

Myometrium highlighted on the Durgical 3D model