Birth defects in the infants of aboriginal and non-aboriginal mothers with diabetes in Western Australia.

OBJECTIVE: Because of the high prevalence of non-insulin-dependent diabetes in Australian Aborigines, and a suggestion that the prevalence of birth defects was high in the infants of Aboriginal mothers with gestational diabetes, this study was undertaken to determine the prevalence of birth defects in infants of Aboriginal and non-Aboriginal mothers with insulin-dependent, non-insulin-dependent, and gestational diabetes mellitus. DESIGN: A retrospective cohort study of all births to diabetic and non-diabetic mothers in Western Australia, 1980-1984. MAIN OUTCOME MEASURE: Birth defects diagnosed at any time up to the age of six years. RESULTS: Compared with infants of non-diabetic, non-Aboriginal mothers, the prevalence ratio for birth defects in infants of non-Aboriginal insulin-dependent mothers was 2.08 (95% confidence interval, 1.2-3.7), and for infants of mothers with non-insulin-dependent diabetes the ratio was 3.64 (95% CI, 1.5-8.6). The corresponding ratios for infants of Aboriginal mothers were 4.85 (95% CI, 0.8-28.2) and 3.64 (95% CI, 1.3-10.4). For birth defects in infants of gestational diabetic mothers, the prevalence ratio was 1.07 (95% CI, 0.6-1.9) for the non-Aboriginal group and 3.65 (95% CI, 2.3-6.0) for the Aboriginal group. Diabetes could have accounted for 0.14% of birth defects in infants of non-Aboriginal mothers and for 4.62% in infants of Aboriginal mothers. CONCLUSIONS: The excess of birth defects in infants of Aboriginal women with gestational diabetes may be due to non-insulin-dependent diabetes that predates the pregnancy but is only diagnosed during pregnancy. For Aboriginal infants, maternal diabetes may be the single most common known cause of birth defects that is amenable to change.