[Twenty years of experience in advanced ultrasound scanning for fetal anomalies in Rotterdam]

At the Rotterdam Fetal Medicine Unit over a period of 20 years, scanning for foetal anomalies has been performed in more than 24,000 pregnancies at risk of a foetal congenital anomaly. In pregnancies where there was prior knowledge of increased risk of a foetal anomaly (group I), the incidence of foetal pathology was 2-5%. In pregnancies in which a foetal anomaly was suspected on clinical or sonographic grounds (group II), the incidence of foetal pathology was 32-57%. For reasons of good-image quality, group I pregnancies were nearly always referred for a foetal-anomaly scan at 18-21 weeks of gestation. Group II pregnancies were often referred after 24 weeks of gestation, which is the upper legal limit for termination of pregnancy in the Netherlands. The detection rate was 94.7% (2000 and 2001). An abnormal chromosome pattern was established in 18% of all affected pregnancies, the great majority of these patterns (83%) being numerical. Approximately 18% of affected pregnancies were discussed in a multidisciplinary setting to ensure correct diagnosis, prognosis and management. Depending on the nature and severity of the foetal anomaly, standard obstetric management was advised in two thirds of cases. In the remaining one third termination of pregnancy was carried out at the request of the parents or a policy of obstetric non-intervention was adopted. In a subgroup comprising 460 pregnant women with both indications for referral, who were investigated at 12-14 weeks gestation, the detection rate for a number of congenital abnormalities was 89.5%.