The influence of prenatal exercise modes on resting maternal blood lactate

Resting lactate concentration in venous blood is a commonly used indicator of metabolic disease risk. Regular exercise during pregnancy improves maternal metabolic health; however, it is unknown if maternal exercise regulates resting lactate concentration. We aimed to elucidate the effects of three different modalities of exercise during pregnancy on blood lactate in pregnant women. This is a secondary analysis of data from three blinded, prospective, randomized controlled trials. Pregnant women were randomized to control or exercise. Exercisers underwent ~24 weeks of supervised aerobic, resistance, or combination exercise between 12–16 and 37–40 weeks gestation. Fasted resting maternal blood lactate was collected at 16 and 36 weeks of gestation. Although lactate increased 0.5 mmol/L in controls across gestation, this rise was blunted in exercisers (p = 0.01). Pre-pregnancy BMI was correlated with blood lactate in controls (p < 0.05, R² = 0.20) but not in exercisers (p > 0.05, R² = 0.01). Exercisers with overweight or obesity had lower 36-week lactate (p = 0.001), particularly in aerobic and combination (p = 0.03; p = 0.006, respectively). These findings show that exercise helps control the BMI-associated rise in maternal lactate seen in gestation and highlights the importance of exercise in women with overweight or obesity.