The primary purpose of this study was to compare maternal plasma inflammation between physically active and inactive obese women during late pregnancy. The secondary purpose was to examine the relationships between maternal plasma inflammation and lipid metabolism and maternal and neonatal metabolic health in these women. A cross-sectional, observational study design was performed in 16 obese-inactive (OBI; means ± SD; age, 25.0 ± 4.8 years; prepregnancy body mass index (BMI), 36.3 ± 4.3 kg/m2; body fat percentage in late gestation, 37.7% ± 3.5%) and 16 obese-active (OBA; age, 28.9 ± 4.8 years; prepregnancy BMI, 34.0 ± 3.7 kg/m2; body fat in late gestation, 36.6% ± 3.8%) women during the third trimester of pregnancy. Maternal plasma inflammation (C -reactive protein (CRP)) and insulin resistance (Homeostatic Model Assessment-Insulin Resistance) were measured at rest. Plasma lipid concentration and metabolism (lipid oxidation and lipolysis) were measured at rest, during a 30-min bout of low-intensity (40% peak oxygen uptake) exercise, and during a resting recovery period using indirect calorimetry. Umbilical cord blood was collected for measurement of neonatal plasma insulin resistance, inflammation, and lipid concentration. Neonatal body composition was measured via air displacement plethysmography. Maternal plasma CRP concentration was significantly higher in OBI compared with OBA women (9.1 ± 4.0 mg/L vs. 6.3 ± 2.5 mg/L, p = 0.02). Maternal plasma CRP concentration was significantly associated with maternal lipolysis (r = 0.43, p = 0.02), baseline lipid oxidation rate (r = 0.39, p = 0.03), and baseline plasma free fatty acid concentration (r = 0.36, p = 0.04). In conclusion, maternal physical activity may reduce inflammation during pregnancy in obese women. Maternal lipid metabolism is related to systemic inflammation.