Maternal protein intake during pregnancy and obesity risk in mothers and offspring: a prospective cohort study.

Background The optimal dietary macronutrient composition during pregnancy to mitigate obesity risk in mothers and offspring remains unclear. Objective To assess associations between maternal dietary macronutrient composition and obesity outcomes in mothers and offspring. Methods We analyzed 66,360 singleton pregnancies from the Danish National Birth Cohort, with dietary intake assessed at gestational week 25. Outcomes included maternal postpartum weight retention(PPWR) at 6 and 18 months and offspring's birth weight, risks of small-for-gestational-age(SGA) and large-for-gestational-age(LGA), BMI z-scores, and overweight/obesity(OWOB) risk at ages 7, 11, and 14 years. Mixture models with response surface visualization examined interactive macronutrient associations, and mixed restricted cubic splines assessed potential non-linear relationships between maternal protein intake and obesity outcomes. Results Mean maternal macronutrient compositions were 15.2% protein, 30.2% fat, and 54.1% carbohydrate. Response surfaces revealed that maternal lower protein intake(%), diluted by higher fat and/or carbohydrate, was associated with higher maternal PPWR at 6 and 18 months but lower birth weight and BMI z-scores in offspring at ages 7, 11, and 14 years. Mixed restricted cubic splines indicated non-linear associations between maternal protein intake(%) and SGA risk(non-linear P=0.003) and LGA(non-linear P=0.04), with a threshold around 15% protein; below this, SGA risk increased while LGA risk decreased. Linear associations were observed for risks of substantial PPWR(PPWR>5kg) and childhood OWOB risk (non-linear P>0.05). Each 5% higher protein intake during pregnancy was related to a lower risk of substantial PPWR at 6 months(OR: 0.90; 95% CI: 0.85, 0.95) and 18 months(0.88; 0.82, 0.94) but higher risks of OWOB at ages 7 years(1.07; 1.01, 1.15) and 11 years(1.11; 1.03, 1.18), with no association at 14 years(1.02; 0.95, 1.10). Conclusions Higher maternal protein intake during pregnancy was associated with lower PPWR and SGA risk but higher LGA and childhood OWOB risks, highlighting potential trade-offs in maternal and offspring obesity outcomes.