Increased risk of macrosomia among overweight women with high gestational rise in fasting glucose.

OBJECTIVES: Maternal overweight is a risk factor for gestational diabetes (GDM) and for newborn macrosomia. Among women without GDM, it is not well understood why some women with high body mass index (BMI) give birth to macrosomic newborns while others do not. We wanted to explore the effect of BMI and fasting plasma glucose (FPG), fasting plasma insulin (FPI) and insulin resistance (HOMA-IR) on the risk of newborn macrosomia.

METHODS: A cohort of 553 Caucasian women was followed throughout pregnancy. The dependent variable was high birth weight (>or=4200 g). Independent variables included gestational age, intake of macronutrients and energy, maternal BMI, weight gain, FPG, FPI and HOMA-IR.

RESULTS: FPG in late pregnancy (30-32 weeks) remained a significant determinant of newborn macrosomia in multiple regression analysis (OR: 1.9, 95% CI: [1.1, 3.4]), whereas FPI and HOMA-IR did not. The women in the highest BMI quartile (>or=27 kg/m(2)) who gave birth to macrosomic newborns had higher increase in FPG and HOMA-IR from early to late pregnancy. Among women in this BMI category, the risk for delivering a macrosomic infant was higher among those with an increase in FPG above 0.60 mmol/l (upper quartile) (OR = 4.5, 95% CI: [1.7, 12.5]).

CONCLUSION: Fasting plasma glucose at week 30-32, but not fasting plasma insulin or insulin resistance, is a determinant of newborn macrosomia. Overweight women with high increase in fasting plasma glucose from early to late pregnancy had a 4.5-fold increase in risk of newborn macrosomia compared to the remaining group with high BMI.