Maternal Energetic Strategies During Pregnancy

Abstract

Human pregnancy is characterized by unique maternal metabolic processes that support the growth and development of a fetus to term. In industrialized nations, the total cost of pregnancy is between 77,000 and 88,000 kilocalories for normal gestational weight gain. Despite the high energy requirement, there appears to be a sustained limit to human energy metabolism, ~2.5 × basal metabolic rate in pregnancy. Yet, variation also exists in maternal environment and lifestyle during pregnancy, and metabolic responses to this variation are not well understood. In this dissertation, I tested predictions of the maternal metabolic limits hypotheses and considered compensatory effects of a maternal constraint on physical activity, body composition, and prenatal and perinatal outcomes. To do so, I analyzed metabolic, anthropometric, physical activity, and health data from a prospective cohort of endurance athletes over pregnancy. I also reviewed previously published data on physical activity and total daily energy expenditure during pregnancy to compare with the athlete cohort. Finally, I analyzed self-reported data on gestational physical activity and pregnancy outcomes from two survey studies. I found evidence for a metabolic limit, ~2.5 × estimated preconception basal metabolic rate, in highly active pregnancies, which may be driven by behavioral and physiological adjustments to keep energy metabolism in check. Endurance athletes had substantially higher levels of physical activity than non-athletes, but similar metabolic scope and energy intake values. Physical activity patterns changed across pregnancy for athletes, which may have affected metabolic costs. Energy compensation and fetal buffering were supported in the trade-off between physical activity and maternal body composition. The prevalence of prenatal and perinatal outcomes also differed between athletes and non-athletes, such that athletes had lower rates of inflammation-based metabolic disorders and delivered smaller neonates. Overall, this dissertation demonstrates that the maternal metabolic limit interacts with environmental and lifestyle factors to influence prenatal and perinatal outcomes for mother and offspring.