Assess the effects of supervised, prenatal aerobic exercise intervention on 1-month-old neonatal morphometry. Secondary data analyses of a 24+ week, randomized controlled exercise intervention trial in pregnant women between 2015 and 2018 were performed. Eligibility criteria included pregnant women: <16 weeks of gestation, singleton pregnancy, aged 18-40 years, and body mass index of 18.5-35.00 kg∙m2 . Eligible pregnant women (n = 128) were randomly assigned a moderate-intensity aerobic exercise group (n = 68) or a nonexercising group (n = 60) consisting of light stretching and breathing techniques. Neonatal weight, skinfold thickness, circumferences, and fat-free mass were measured at 1-month of age. Covariates included weight gain, gestational diabetes mellitus, and neonatal sex. ANCOVAs for intention-to-treat (ITT) and per protocol were performed. ITT and per protocol analyses included 74 and 56 participants, respectively. Adjusted regression results showed significant between-group differences for neonatal skinfold thickness (ITT: 20.0 mm vs. 22.2 mm; p = .04; per protocol: 19.8 mm vs. 22.3 mm; p = .03) and body fat (per protocol 13.2% vs. 15.1%; p = .05). No between-group differences for weight (p = .36, .25), abdominal (p = .08, .35) and mid-upper arm circumferences (p = .30, .26), or fat-free mass (p = .83, .69). The study findings suggest that aerobic exercise has a beneficial impact on neonatal skinfold thickness and percent body fat at 1 month of age. Participation in the recommended levels of aerobic exercise (150 min, moderate-intensity per week) throughout the prenatal period may serve as an effective strategy to reduce the risk of overweight or obesity in the early postnatal period.