Accreta placentation

• Placental lacunae are large, irregular sonolucent intraplacental spaces giving the placenta a moth-eaten appearance
• Lacunae are the most common ultrasound sign in PAS
• They are distorted cotyledons and interlobular septa
• Lacunae have direct high velocity maternal blood from a radial or arcuate artery. The peak systolic velocity is often >10 cm/sec
• Their shape is not influenced by the filling of the bladder or pressure from the probe

The difference between the appearance of lacunae in PAS and placental lakes in a normal placenta may not always be clear cut, but lacunae are larger, more irregular, contain high velocity turbulent blood flow.