Congenital malformations in the southeast of Sweden-a registry study with validation

A study was made of the occurrence of congenital malformations in the southeast region of Sweden, utilizing all available relevant health registries. Östergötland county had been pinpointed in a routine surveillance as having an increased malformation risk. Various validations of the register data were undertaken and different types of errors were detected. An increased risk was seen, in Östergötland county compared to the reference counties, for specific types of malformations: preauricular appendices, pylorostenosis, uterine/vaginal malformations, foot deformities, limb reduction defects and cardiovascular malformations. Variable classification or registration artefacts explained the excess among the first four conditions. Limb reduction defects were also mis‐coded, but the increased risk in Östergötland county may persist. Conclusion: There is an increased risk of major cardiovascular malformations in Östergötland county compared to the reference counties that also shows an uneven distribution within the county.