The Effectiveness of Ultrasound Screening at 18-20 Weeks Gestational age for Prediction of Placenta Praevia

Summary In a retrospective study of 4300 ultrasound scans for placental localisation 505 patients were described as having 'low-lying' placentas on a scan performed at 18-20 weeks pregnant. When these were divided into two groups with the placenta covering or not covering the cervical os, it was found that only the former group were at significant risk of developing a placenta praevia (41.4 per cent) or of having an antepartum haemorrhage (27.6 per cent). It is therefore suggested that only these cases should be the subject of repeated scanning at 32 weeks to screen for placenta praevia.