Ultrasound screening in the middle trimester of pregnancy: The identification of multiple pregnancy, fetal abnormality and pregnancies resulting in middle trimester loss

SummaryAs part of a survey examining the value of a policy of middle trimester screening ultrasound scanning, pregnancies delivered after 19 weeks of pregnancy and resulting in twins, a significant structural fetal abnormality, or a non-viable fetus at less than 28 weeks were studied.In only 3 of 14 twin pregnancies had the diagnosis been suspected clinically. All were diagnosed by a middle trimester scan, although one had been missed on a first trimester scan.Five of 10 structural fetal abnormalities were not detected by the screening scan, including one menin-gomyelocoele. There were no false positive diagnoses of fetal abnormalities by ultrasonography.Recurrent bleeding in early pregnancy was the best predictor of late middle trimester abortion but in all five cases who had two scans in the first half of pregnancy, there was a fall off in fetal growth parameters between the scans. A much larger sample would be needed to confirm or refute this trend.