Routine radiographer screening for fetal abnormalities by ultrasound in an unselected low risk population.

A screening programme for fetal abnormalities began at The Hillingdon Hospital in July 1986. Second trimester ultrasound scans are performed by radiographers. A combined prospective and retrospective study of the ultrasound findings and outcome in all pregnancies delivered in 1989-1990 was undertaken. 6412 babies were born during this period, of whom 6183 (96%) were examined by ultrasound in the second trimester; 29 pregnancies were terminated for fetal abnormality. Of the 89 fetuses who were abnormal at birth or at induced termination of the pregnancy (1.4%), 84 were scanned in the second trimester. In 51 cases the abnormality was detected before 22 weeks gestation (sensitivity, 60.7%). 56 of these 84 abnormal fetuses scanned had potentially lethal or major handicapping abnormalities of which 41 were detected by ultrasound before 22 weeks gestation (sensitivity, 73%). There was one false positive diagnosis of abnormality which did not affect outcome. 6352 babies were normal at delivery or on discharge from hospital (specificity, 99.98%).