Changes in maternal blood glucose and lipid concentrations during pregnancy differ by maternal body mass index and are related to birthweight: A prospective, longitudinal study of healthy pregnancies

Background Maternal obesity is increasing worldwide but the consequences for maternal physiology and fetal growth are not fully understood. Objective To study whether changes in glucose and lipid metabolism during pregnancy differ between women with normal weight and overweight/obesity, and investigate which of these metabolic factors are associated with birthweight. Design Prospective, longitudinal study. Setting Department of Obstetrics, Oslo University Hospital, Rikshospitalet. Population 1031 healthy pregnant women with singleton pregnancies. Methods Blood samples from early and late pregnancy were analyzed for fasting glucose, insulin and lipids (total cholesterol, HDL-cholesterol, LDL-cholesterol and triglycerides). Associations between metabolic factors and birthweight (z-scores) were explored by linear regression models. Main Outcome Measures: Group-dependent longitudinal changes in glucose and lipids and their association with birthweight (z-scores). Results Compared to women with normal weight (BMI < 25), women with overweight (BMI 25-29.9) and obesity (BMI > 30) had significantly higher fasting glucose (4.54, 4.68 and 4.84 mmol/l), insulin (23, 33 and 50 pmol/l), total cholesterol (4.85, 4.99 and 5.14 mmol/l), LDL-C (2.49, 2.66 and 2.88 mmol/l) and triglycerides (1.10, 1.28 and 1.57 mmol/l), but lower HDL-C (1.86, 1.75 and 1.55 mmol/l). BMI (B 0.05, 95% CI 0.03-0.06, p<0.001), gestational weight gain (GWG) (B 0.06, 0.05-0.08, p<0.001) and an increase in fasting glucose (B 0.30, 0.16-0.43, p<0.001) were positively associated with birthweight, whereas a decrease in HDL-C (B -0.72, -0.96- -0.53, p<0.001) had a negative association with birthweight. Conclusions Overweight/obesity was associated with an unfavorable metabolic profile in early pregnancy which was associated with increased birthweight. However, modifiable factors like gestational weight gain and an increase in fasting glucose were identified and can be targeted for interventions.