Maternal Weight, Placental Expression of Growth Factors, and Birth Weight

Background: Low and high infant birth weight are associated with adverse health outcomes such as infant mortality during the first year of life, developmental problems in childhood, and risk of disease in adulthood. Maternal weight (body mass index [BMI] and gestational weight gain [GWG]) are known to be strong predictors of infant birth weight. However, the biological mechanisms underlying the relationships among maternal weight, gene expression, and infant birth weight are still poorly understood. Objective: This study aimed to identify predictive relationships among maternal weight (BMI and GWG), placental gene expression of vascular endothelial growth factor (VEGF) A and placental growth factor (PlGF), and infant birth weight. The overall hypothesis was that VEGF-A and PlGF mRNA mediate the predictive relationships of maternal weight (BMI and GWG) with infant birth weight. Methods: Placentas were collected at delivery from healthy women (n = 44). RNA was extracted, and VEGF-A and PlGF expression was quantified using quantitative real-time polymerase chain reaction. Multiple regression models and path analysis were used to identify predictive relationships among variables. Results: PlGF mRNA level (p = .04) was a significant predictor of infant birth weight. Three covariates, age (p = .01), placental weight (p < .001), and Black race (p = .04), were also predictors of infant birth weight, whereas BMI was not a significant predictor. GWG and VEGF-A mRNA level did not independently predict infant birth weight; rather, GWG significantly modified the effect of VEGF-A mRNA level on infant birth weight. Neither VEGF-A nor PlGF mRNA was a mediator between maternal weight (BMI and GWG) and infant birth weight. Conclusion: This study indicates that the relationships among maternal weight (BMI and GWG), placental expression of VEGF-A and PlGF, and infant birth weight can be partially explained by placental biological pathways, specifically angiogenesis and inflammatory pathways. Although these findings are noteworthy, the relationships among maternal weight, placental gene expression, and infant birth weight require further investigation to more fully identify their underlying mechanisms.