Experimental data on the effects of lifestyle interventions on fetal neurodevelopment in humans remain scarce. This study assessed the impact of a pregnancy nutrition+exercise intervention on offspring neurodevelopment at 12 months of age. The Be Healthy in Pregnancy (BHIP) randomized controlled trial (RCT) randomly assigned pregnant persons with stratification by site and body mass index (BMI) to bi-weekly nutrition counselling and high dairy protein diet, walking goal of 10,000 steps/day plus usual prenatal care (UPC; intervention group) or UPC alone (control group). This study examined a subset of these mothers (> 18 years, singleton pregnancy, BMI <40 kg/m2, and enrolled by ≤12 weeks gestation) and their infants (intervention = 42, control = 32), assessing cognition, language, motor, social-emotional, and adaptive functioning at 12 months using the
Bayley Scales of Infant and Toddler Developmentthird edition (BSID-III) as the outcome measure. We also examined if maternal factors (prepregnancy BMI, gestational weight gain (GWG)) moderated associations. Expressive language (MD = 9.62, 95% CI = (9.05–10.18), p= 0.03, ƞ2 p= 0.07) and general adaptive composite (GAC) scores (MD = 103.97, 95% CI = (100.31–107.63), p= 0.04, ƞ2 p= 0.06) were higher in infants of mothers in the intervention group. Effect sizes were medium. However, mean cognitive, receptive language, motor, and social-emotional scale scores did not differ between groups. A structured and monitored nutrition+exercise intervention during pregnancy led to improved expressive language and general adaptive behavior in 12-month-olds, but not cognitive, receptive language, motor, or socioemotional functioning. While these experimental data are promising, further research is needed to determine the clinical utility of nutrition+exercise interventions for optimizing infant neurodevelopment.