Background: Gestational diabetes mellitus (GDM) is associated with adverse birth outcomes, including higher infant adiposity, elevated Ponderal Index (PI), higher weight-to-length ratio, and increased risk of cesarean delivery. Supervised prenatal exercise may improve birth outcomes, potentially mitigating GDM-related complications; however, it remains unclear whether birth outcomes differ between women with and without GDM who participate in a structured, supervised exercise program throughout pregnancy. Objective: The purpose of this study was to examine differences in birth outcomes between pregnant women with and without GDM who participated in a supervised prenatal exercise program. We hypothesized that women with GDM engaging in supervised exercise would demonstrate similar birth outcomes as exercising women without GDM. Methods: This is a secondary analysis of a prospective, randomized exercise intervention trial. A total of 370 pregnant women (GDM: n = 22; Non-GDM: n = 348) were enrolled at ?16 weeks of gestation and participated in supervised exercise (aerobic, resistance, combination, or control group) three times per week until delivery. Exercise variables included total training sessions, weekly frequency, duration, intensity (metabolic equivalents; METs), and total exercise volume (MET-min). Infant birth outcomes were abstracted from medical records and included birth weight, birth length, weight-to-length ratio, infant body mass index (BMI), Ponderal Index, head, chest, and abdominal circumferences, head circumference-to-abdominal circumference ratio (HC:AC), Apgar scores, gestational age at birth, and delivery mode. Between-group differences were assessed using t-tests. Results: GDM and Non-GDM groups were similar across all birth outcomes (all p > 0.05), including birth weight (3.42 ± 0.54 kg vs. 3.42 ± 0.56 kg, p = 0.99), infant BMI (14.00 ± 1.76 vs. 14.23 ± 1.81, p = 0.57), and Ponderal Index (28.44 ± 4.10 vs. 29.07 ± 3.59, p = 0.51). Regression analyses revealed that total pregnancy training sessions are a significant positive predictor of birth weight (? = 0.17, p = 0.05), weight-to-length ratio, infant BMI, and Ponderal Index, while exercise intensity is a significant negative predictor of weight-to-length ratio, infant BMI, and Ponderal Index (all p < 0.05). GDM treatment type was not a significant predictor in any model. Conclusion: Pregnant women with and without GDM who participated in a supervised prenatal exercise program demonstrated similar birth outcomes across all measures, supporting the hypothesis that supervised exercise helps normalize birth outcomes regardless of GDM status. These results add to the body of evidence supporting clinicians’ advice that women with gestational diabetes engage in supervised prenatal exercise while considering factors such as training frequency, exercise intensity, and availability of safe resources.