Three infants of diabetic mothers with malformations of left-right asymmetry--further evidence for the aetiological role of diabetes in this malformation spectrum.

We report three babies with malformations of left-right asymmetry who were born to mothers with insulin-dependent diabetes mellitus. One infant had left isomerism and asplenia, one had polysplenia, and the third baby had situs inversus with a neural tube defect. Defects of left-right asymmetry have not previously been well recognized as part of the spectrum of anomalies associated with maternal diabetes. We believe that the association of maternal diabetes with these malformations in the infants is not coincidental, and that diabetes mellitus has an aetiological role in this spectrum of abnormalities. Two of the mothers had elevated HbA1C levels in pregnancy, and thus the malformations may be due to poor glycaemic control, although other teratogenic mechanisms associated with diabetes cannot be excluded. Finally, to our knowledge, the finding of left isomerism with asplenia (part of the spectrum of right isomerism) is rare. The occurrence of both forms of isomerism in different parts of the same body supports the model of random development of laterality following the interruption of normal developmental processes.