The development of high-resolution real-time ultrasound has created the opportunity to identify fetal congenital anomalies. Making this technique part of a screening activity must be based on the belief that early identification and early care will have a favourable impact on the natural history of the disease. This is not the case when pregnancies are screened in the second trimester to detect malformations. On the contrary; in Norway, this might lead to the yearly elimination of 300 desired fetuses. Some of these would otherwise have had a longer intrauterine life, some might have benefited from postnatal medical treatment and some might otherwise have been born as healthy children instead of being eliminated due to misclassification.