Maternal Adipose Tissue Expansion, A Missing Link in the Prediction of Birth Weight Centile

Context Maternal body mass index (BMI) is associated with increased birth weight but does not explain all the variance in fetal adiposity. Objective To assess the contribution of maternal body fat distribution to offspring birth weight and adiposity. Design Longitudinal study throughout gestation and at delivery. Setting Women recruited at 12 weeks of gestation and followed up at 26 and 36 weeks. Cord blood was collected at delivery. Patients Pregnant women (n = 45) with BMI 18.0 to 46.3 kg/m2 and healthy pregnancy outcome. Methods Maternal first trimester abdominal subcutaneous and visceral adipose tissue thickness (SAT and VAT) was assessed by ultrasound. Main Outcome Measures Maternal body fat distribution, maternal and cord plasma glucose and lipid concentrations, placental weight, birth weight, and fetal adiposity assessed by cord blood leptin. Results VAT was the only anthropometric measure independently associated with birth weight centile (r2 adjusted 15.8%, P = .002). BMI was associated with trimester 2 and trimesters 1 through 3 area under the curve (AUC) glucose and insulin resistance (Homeostatic Model Assessment). SAT alone predicted trimester 2 lipoprotein lipase (LPL) mass (a marker of adipocyte insulin sensitivity) (11.3%, P = .017). VAT was associated with fetal triglyceride (9.3%, P = .047). Placental weight was the only independent predictor of fetal adiposity (48%, P < .001). Maternal trimester 2 and AUC LPL were inversely associated with fetal adiposity (r = -0.69, P = .001 and r = -0.58, P = .006, respectively). Conclusions Maternal VAT provides additional information to BMI for prediction of birth weight. VAT may be a marker of reduced SAT expansion and increased availability of maternal fatty acids for placental transport.