Context & Objective A recent paper by our group reported that regular aerobic exercise during pregnancy led to lower foetal IGF-I and IGF-II concentrations and a modest reduction in offspring birth weight when compared with the offspring of nontraining control participants. Maternal hormonal alterations in response to exercise training may be associated with the regulation of nutrient availability for foetal growth through placental regulation of maternal metabolism.
Objective To determine whether the reduction in offspring size was associated with changes in the maternal IGF axis [including placental growth hormone (PGH)], leptin and/or free fatty acids (FFA) in response to aerobic exercise training in the second half of pregnancy.
Design and Setting A randomized, controlled trial of exercise in pregnancy.
Patients Eighty-four healthy nulliparous women (mean ± SD age 30 ± 4 year, BMI 25·5 ± 4 kg/m2).
Measurements Serum samples were drawn at 19 and 35 weeks gestation to determine serum IGF-I, IGF-II, IGF-binding protein-1, IGF-binding protein-3, PGH, leptin and FFA.
Results Exercise training in pregnancy had no impact on the pregnancy-related changes in the maternal IGF axis. Women in the exercise group experienced a 29% increase in leptin in late gestation (P = 0·026 vs control) and a trend towards lower FFA (P = 0·07 vs control). Late pregnancy changes in maternal leptin were inversely related to offspring birth weight (r = −0·24, P < 0·05) and BMI (r = −0·25, P < 0·05).
Conclusions An increase in leptin in exercising pregnant women may reflect subtle changes within the placenta in response to regular exercise and may contribute to the reduction in offspring size previously reported in this cohort.