Physical Activity During Pregnancy and Gestational Weight Gain: Implications for Maternal–Fetal Epigenetic Programming and Long-Term Health

Background/Objectives: Gestational weight gain (GWG) is a crucial factor influencing mother and fetal health, as high GWG is associated with adverse pregnancy outcomes and an increased long-term risk of obesity and metabolic issues in the children. In addition to controlling weight, maternal physical activity (PA) during pregnancy may influence fetal development through potential epigenetic mechanisms, including histone modifications, DNA methylation, and the production of non-coding RNA. Methods: This narrative review synthesizes evidence from randomized controlled trials (RCTs; n = 11, 3654 participants) investigating the impact of aerobic PA on GWG, while also highlighting emerging, primarily indirect findings on maternal–fetal epigenetic programming. Results: The majority of RCTs found that supervised PA interventions, especially when paired with nutritional counseling, decreased both the incidence of excessive GWG and total GWG. Enhancements in lipid metabolism, adipokine profiles, and maternal insulin sensitivity point to likely biochemical mechanisms that connect PA to epigenetic modification of fetal metabolic genes (e.g., IGF2, PGC-1α, LEP). Animal and observational studies suggest that maternal activity may influence offspring epigenetic pathways related to obesity and cardiometabolic conditions, although direct human evidence is limited. Conclusions: In addition to potentially changing gene–environment interactions throughout generations, prenatal PA is a low-cost, safe method of improving maternal and newborn health. Future RCTs ought to incorporate molecular endpoints to elucidate the epigenetic processes by which maternal exercise may provide long-term health benefits.