Placenta Accreta MRI — Assessing the Invasive Placenta

Placenta Accreta MRI

When the placenta grows abnormally into the uterine wall, delivery becomes high-risk — MRI helps map how deep and how far it goes so the surgical team can plan.

The problem

In placenta accreta spectrum (PAS), placental tissue invades abnormally into (accreta), through (increta) or beyond (percreta) the myometrium, risking catastrophic haemorrhage at delivery. Ultrasound is first-line; MRI is added for problem-solving — posterior placentas, assessing depth, and mapping extent (e.g. bladder/parametrial involvement).

MRI doesn’t replace ultrasound — it answers the harder questions of depth and topography that change the surgical plan.

Key MRI signs

Dark intraplacental bands on T2 (thick, irregular).
Myometrial thinning/loss and abnormal uterine bulging.
Bladder-wall interruption or tenting (percreta).
Abnormal placental vascularity and heterogeneity.

Imaging is performed without gadolinium (avoided in pregnancy) using fast T2 sequences.

Why it matters

Accurate mapping enables planned delivery in a specialist centre with the right team, blood products and surgical strategy (often planned caesarean hysterectomy), markedly improving safety. Risk factors include prior caesarean and placenta praevia — the combination should prompt careful assessment.

Reference: Jha P et al. Society of Abdominal Radiology/ESUR joint consensus on MRI of placenta accreta spectrum. Eur Radiol 2020;30:2604–15.

Educational summary for clinicians; managed by specialist maternal-fetal teams. Not medical advice.