Interactions between maternal health and placental morphology on neonate body composition.

Background: We aimed to examine maternal metabolic correlates of neonate body composition, and the potential mediating effect of the placenta. Methods: Data were collected throughout pregnancy and at delivery. An oral glucose tolerance test (OGTT) was conducted in order to diagnose or rule out gestational diabetes mellitus (GDM). Maternal weight and blood pressure were taken and hypertension and gestational weight gain (GWG) were defined. Gestational age, birth weight (BW) and weight to length ration (WLR) were recorded. Photographs were taken of the placenta, and the widths and lengths were measured digitally. Body composition was analysed via air displacement plethysmography or dual-energy x-ray absorptiometry. Mediation models were conducted to determine the mediation effect of the placental variables on the relationships between maternal health variables and neonate outcomes. Next, interaction terms were added to models to determine how maternal and placental variables interacted in their effect on neonate outcomes. Results: A total of n = 280 women were included in the analysis. Majority were overweight or obese. Fourteen percent of women developed GDM during pregnancy, 5% had hypertension during pregnancy, 32% were HIV positive, and 32% had anemia. For the birth weight outcome, coefficients of BMI were attenuated by the addition of placental variables (Model 1 ß=18.66 vs Model 2 ß=16.40). Similar patterns were evident for GWG and hypertension, and for the WLR outcome. In all cases the addition of the placental variables attenuated associations between maternal exposures and neonatal outcomes, yet the level of significance did not change. Inclusion of interaction terms reversed the direction of the relationships between hypertension and BW and WLR, and between GWG and WLR. Conclusion: The placenta buffers some harmful effects of obesity, GWG, and hypertension on neonate size, and placental efficiency interacted with most maternal risk factors to either counteract, or attenuate relationships with neonate size at birth. However the placenta was unable to completely counteract the negative effect of excess nutrient supply on in utero growth.