Mediators linking maternal weight to birthweight and neonatal fat mass in healthy pregnancies.

Lifestyle interventions have not efficaciously reduced complications caused by maternal weight on fetal growth, requiring insight into explanatory mediators.We hypothesized that maternal mediators, including adiponectin, leptin, insulin, and glucose, mediate effects of pregestational BMI (pBMI) and gestational weight gain (GWG) on birthweight and neonatal fat mass percentage (FM%) through placental weight and fetal mediators, including insulin levels ([I]fv) and venous-arterial glucose difference (Δ[G]fva). Hypothesized confounders were maternal age, gestational age, and parity.A cross-sectional study of healthy mother-offspring-pairs (n=165) applying the 4-vessel in vivo sampling method at Oslo University Hospital, Norway.We obtained pBMI, GWG, birthweight, and placental weight. FM% was available and calculated for a subcohort (n=84). We measured circulating levels of adiponectin, leptin, glucose, and insulin and performed path analysis and traditional mediation analyses based on linear regression models.The total effect of pBMI and GWG on newborn size was estimated to 30(16, 45)g birthweight and 0.17(0.04, 0.29)FM% per kg∙m -2 pBMI and 31(18, 44)g and 0.24(0.10, 0.37)FM% per kg GWG. The placental weight was the main mediator, mediating 25g birthweight and 0.11FM% per kg∙m -2 pBMI and 25g birthweight and 0.13FM% per kg GWG. The maternal mediators mediated a smaller part of the effect of pBMI (3.8g birthweight and 0.023FM% per kg∙m -2 pBMI) but not GWG.Placental weight was the main mediator linking pBMI and GWG to birthweight and FM%. The effect of pBMI, but not GWG, on birthweight and FM%, was also mediated via the maternal and fetal mediators.

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Authors: Oddrun Kristiansen, Manuela Zucknick, Trine M Reine, Svein O Kolset, Thomas Jansson, Theresa L Powell, Guttorm Haugen, Tore Henriksen, Trond M Michelsen