[The standard mid-pregnancy anomaly scan in the Netherlands: what is its effect?].

- The mid-pregnancy anomaly scan was introduced into the Netherlands in 2007. The scan is performed at 18- 21 weeks of pregnancy.- The detection rate of open spina bifida is 94%.- In the Netherlands, 60% of all congenital heart defects are diagnosed prenatally compared with 35-40% in other countries. There is a strong relationship between the severity of the heart defect and the detection rate, as more than 95% of all univentricular heart defects are detected.- The detection rate of isolated cleft lip and cleft palate has increased from 32% to 87%.- The absolute number of abortions has not increased since the implementation of the anomaly scan. However, perinatal morbidity and mortality have decreased.- To further increase the quality of the screening programme, prenatal and postnatal congenital defect registries should be linked and studies into the effect of intensive training of sonographists with modern teaching methods should be performed.