[Study of the Danish Malformation Registry for the incidence of cleft lip and palate during 1983-1987].

The Danish Register of Congenital Malformations at the National Board of Health is used for surveillance and research. More than 10% of all patients registered have oral cleft diagnoses. This report evaluates the completeness of the Register of Congenital Malformations as regards registration of oral cleft patients born in Denmark in the period 1983-1987. The register is limited to congenital anomalies diagnosed in hospitals in the child's first year of life. The investigation shows, that the register is suitable for surveillance of clefts, because the completeness of registration was constant during the five-year period 1983-1987. The completeness was more than 90% of all known cases, and probably higher for severe clefts and cases with associated anomalies. Identical diagnosis was found in 93% of all patients registered in The Register of Congenital Malformations with at least one other source of ascertainment. In addition, the investigation disclosed misclassification of a small oral-cleft-subgroup and the need for an additional diagnosis in the coding. The register can only be used for surveillance and research in congenital anomalies, which are usually diagnosed in the child's first year of life.