Surveillance of congenital malformations and other conditions of the newborn.

A brief description is given of a birth defects monitoring system in operation on a monthly basis in Norway since 1 January 1971. The system has disclosed apparent epidemic increases in congenital dislocation of hip and anomalies of the limbs, caused by changes in registration practice. An increase in the registration of anomalies of the uro-genital system, that started in the autumn of 1972, is currently being investigated in depth through a case-control study covering all cases of hypospadias and undescended testicles that are registered in the total population of births in Norway. However, this population is too small to provide a quick answer to urgent questions. To overcome this obstacle international collaboration is essential.