The epidemiology of preaxial limb malformations.

The epidemiology of preaxial limb malformations was studied in an effort to find similarities and differences between different types that could help to define suitable groups of malformations for etiologic studies. Material from three large congenital malformation registers was used, with a total of 1646 infants with such malformations among over 5 million births. We compared different types of preaxial malformations with respect to bilaterality, maternal age and parity, racial differences, sex distribution, twinning, and associated malformations. From many epidemiologic aspects, different types of preaxial malformations showed similarities, but there were some distinct differences between upper and lower limb anomalies. We conclude that in searches for etiologic factors, it may be useful to group all preaxial malformations together but to differentiate between upper and lower limb defects.