Neonatal Outcomes Following a Preconception Lifestyle Intervention in People at Risk of Gestational Diabetes: Secondary Findings from the BEFORE THE BEGINNING Randomized Controlled Trial

<b>Objectives:</b> Gestational diabetes mellitus (GDM), particularly when combined with overweight or obesity, is associated with adverse neonatal outcomes such as high birth weight and increased adiposity. We determined the effect of a preconception lifestyle intervention initiated before and continued throughout pregnancy on neonatal, birth-related, and body composition outcomes at birth and 6-8 weeks of age in children of participants in the BEFORE THE BEGINNING randomized controlled trial. <b>Methods:</b> People (<i>N</i> = 167) at increased risk of GDM and planning pregnancy were randomly allocated 1:1 to intervention or control. The intervention included time-restricted eating and exercise training. Time-restricted eating involved consuming all energy within ≤10 h/day, ≥5 days per week, and the amount of exercise was set using a heart rate-based physical activity metric (Personal Activity Intelligence, PAI), with the goal of ≥100 weekly PAI points. The main outcome of interest in this report was the proportion of infants with birth weight > 4.0 kg. <b>Results:</b> Among 106 live births, 21% (11/53) of infants in the intervention group and 28% (15/53) in the control group had birth weight > 4 kg (<i>p</i> = 0.367). Mean birth weight did not differ significantly between groups (mean difference -159.3 g, 95% confidence interval -375.7 to 57.2, <i>p</i> = 0.148). No significant between-group differences were found for additional neonatal, birth-related, or early postnatal body composition outcomes. <b>Conclusions:</b> In this secondary analysis, we found no evidence of effects of a preconception lifestyle intervention on the risk of macrosomia or neonatal body composition.