Birth weight of women with gestational diabetes.

OBJECTIVE: Epidemiological observations have suggested a relationship between type 2 diabetes and a low birth weight. However, there are many confounding variables and problems with retrospective data collection. Women with gestational diabetes mellitus (GDM), who are likely to develop type 2 diabetes in the future, may help clarify these observations. RESEARCH DESIGN AND METHODS: Consecutive women with GDM (n = 138) were included in the study if they had a singleton pregnancy delivered between 37 and 41 weeks of gestation, if they had themselves been born in the local hospital, and if their own delivery data were available. With respect to their own births, a matched group was obtained by considering the next female delivery of the same gestational age. RESULTS: For women with GDM, the mean (+/- 1 SD) birth weight was 3,293 +/- 493 g and the ponderal index was 27.0 +/- 2.4. Their values were not significantly different from the matched group, which had a birth weight of 3,315 +/- 460 g and a ponderal index of 27.0 +/- 2.5. After adjusting for the gestational age of delivery, the birth weight of women with GDM did not show a U-shaped distribution. CONCLUSIONS: After adjustment for the gestational age of delivery, women with GDM do not themselves have either a lower or higher birth weight than a matched group. These data suggest that women with GDM are either not a good surrogate for investigating the relationship between birth weight and type 2 diabetes or that correction for the gestational age of delivery removes the most important confounding variable. It is also possible that modern dietary changes may have altered the relationship.