Relationship between gestational diabetes mellitus and low maternal birth weight.

Objective: To study the relationship between low birth weight and the presence of gestational diabetes mellitus (GDM) or peripheral insulin resistance during pregnancy.

Research Design And Methods: We studied the relationship between peripheral insulin sensitivity (calculated by Matsuda and DeFronzo's oral glucose tolerance test (OGTT)-derived insulin sensitivity index [ISI(OGTT)]) or GDM prevalence and birth weight in 604 pregnant women, classified as normally glucose tolerant (n = 462) or affected with GDM (n = 142) after a 100-g 3-h oral glucose tolerance test. We then categorized these subjects into two groups: individuals with birth weight in the <10th percentile (<2,600 g; n = 68) and individuals with birth weight in the >10th percentile (n = 536).

Results: GDM prevalence was higher in the group in the lowest birth weight decile (<2,600 g; 24/68; 35%) than in the group with normal/high birth weight (118/536; 22%; chi(2) = 5.917; P = 0.01). Relative risk for GDM adjusted for age, parity, family history of diabetes, and prepregnancy body weight was about twofold in the group with low birth weight (odds ratio = 1.89 [95% CI 1.088-3.285; P = 0.023]), and the prevalence of low birth weight was about threefold higher in the first ISI(OGTT) decile. In 450 women whose newborn's weight was known, the delivery of macrosomic babies was associated with a twofold higher relative risk for GDM in women who themselves had low birth weight. In the latter, the relationships between their newborn's weight and either maternal glucose tolerance (positive) or ISI(OGTT) (negative) were amplified.

Conclusions: Low maternal birth weight was associated with a twofold higher risk for GDM, independent of major confounders. Such a risk was highest in women with low birth weight who delivered macrosomic babies, and in the group with low birth weight, the relationship between maternal glucose tolerance or insulin resistance and offspring's neonatal weight was much more evident.