A modified method for the epidemiological analysis of registry data on infants with multiple malformations

Background Infants with multiple malformations are important in birth defec t epidemiology and malformation monitoring because human teratogens have of ten caused complex malformations. Various methods for the analysis of multi malformed infants have been tried. Methods By using data from four large registries of congenital malformation s, 5256 infants were identified with two or more among 73 selected malforma tions. Pairwise associations between malformations were detected by multipl e logistic regression analyses, and putative confounders (programme, matern al age, autopsy, etc.) were controlled for. For each significant pairwise a ssociation, further analyses were performed in order to find associations w ith a possible third malformation. Results The importance of controlling for several confounders was demonstra ted. Several well-known associations were found, which supports the techniq ue used. The interpretation of three-way associations was discussed. Result s from the present study were compared with those obtained using some other methods. Conclusions Different confounders can cause biased associations. The method presented in the paper takes this into consideration and is therefore more likely than previously used techniques to give unbiased information on the clustering of different malformations among multimalformed infants.