Gestational diabetes and fetal macrosomia: a dissenting opinion.

Objectives: To examine the effect of interaction between parity, overweight/obesity, gestational weight gain, and gestational diabetes mellitus (GDM) on the incidence of fetal macrosomia.

Methods: We used a population-based dataset to establish the incidence of macrosomia (birth weight >4000 g) in singleton births at ≥38 weeks' gestation. The cohort included women who were (1) overweight/obese or had normal body mass index (BMI) before pregnancy, (2) nulliparous or multiparous, (3) with appropriate or excessive weight gain, and (4) without GDM, with GDM controlled by nonpharmacological treatment (GDM0), or with GDM requiring insulin treatment (GDM1).

Results: We examined 129 686 births at ≥38 weeks. The mean gestational age at birth for all subgroup was similar. When compared with a reference incidence for nulliparas with normal pregravid BMI, appropriate weight gain, and without GDM, all variables, except GDM, independently and significantly increased the incidence of neonates weighing >4000 g. The logistic regression analysis found that excessive weight gain, pregravid BMI >25, and parity were the only independent factors associate with birth weight >4000 g.

Conclusions: Well-managed GDM is not significantly associated with macrosomia, whereas pre-pregnancy obesity, excessive gestational weight gain, and parity appear to be significant risk factors. These results emphasize the need for effective weight management before and during pregnancy to reduce the risk of fetal overgrowth.