Objective: To compare outcomes of pregnancies complicated by gestational diabetes mellitus (GDM) in underweight women with those of normal pregravid BMI.Methods: We used a population-based dataset to identify singleton pregnancies complicated by GDM in underweight and normal weight women.Results: Among women with GDM, we identified 301 and 6494 women with pregravid underweight and normal BMI. Underweight women were younger, more often nulliparous, and had lower birth weight (p < .05) and lower incidence of birth weight > 4000 g (OR 0.3, 95% CI 0.1, 0.6) as compared to normal weight GDM women.Conclusions: It appears that pregravid maternal weight rather than GDM might be responsible for larger babies. A dose-response relationship should be established, however.
Keywords: Gestational diabetes mellitus; macrosomia; underweight.