Incidence and secular trends of congenital limb defects in Finland.

The total incidence rate of three selected congenital limb defects was 12.8 per 10 000 births in Finland from 1964 to 1977; 1235 cases were reported to the Registry of Congenital Malformations. The incidence rate of reduction limb deformities was 5.0 per 10 000 births (481 cases), of polydactyly 5.8 (559) and of syndactyly 3.1 (299), respectively. The total incidence rate and the rates for all the subgroups had a statistically significant increasing trend even after the incidence rates were compared to the reporting rate of all malformations (p less than 0.01). No significant variations in seasonal distributions were found. In 69% of the reduction deformities only one or both upper limbs were affected, 20% of the children had only lower limb defects, and 11% of the cases had defects in both upper and lower limbs. In 28% of the cases additional malformations were reported. For comparison, incidence rates of the selected limb defects from 13 other national surveillance systems are presented.