Placenta Accreta Index (PAI) Calculator Placenta Accreta Index (PAI) Calculator Prior Cesarean Deliveries < 2 Prior Cesareans (+0) ≥ 2 Prior Cesareans (+3.0) Placental Location Other than Anterior Previa (+0) Anterior Placenta Previa / Low Lying (+1.0) Placental Lacunae (Finberg Grade) Grade 0: None (+0) Grade 1: 1–3 small lacunae (+0) Grade 2: 4–6 larger/irregular lacunae (+1.0) Grade 3: Many large, bizarrely shaped lacunae (+3.5) Smallest Myometrial Thickness > 5 mm (+0) > 3 mm to ≤ 5 mm (+0.25) > 1 mm to ≤ 3 mm (+0.5) ≤ 1 mm (+1.0) Bridging Vessels (Color Doppler) Absent (+0) Present (+0.5) Total PAI Score: 0.0 Predicted Probability of Invasion: < 5% Low risk profile.
