Longitudinal assessment of energy balance in well-nourished, pregnant women

Background: Clinicians often recommend an additional energy intake of 1250 kJ/d to their pregnant patients. Previous studies have shown considerable v ariation in the metabolic response to pregnancy and thus in the additional energy required to support a pregnancy. Objective: The purpose of this study was to assess how well-nourished women meet the energy demands of pregnancy and to identify factors that predict an individual's metabolic response. Design: Resting metabolic rate (RMR), diet-induced thermogenesis (DIT), tot al energy expenditure (TEE), activity energy expenditure (AEE), energy inta ke (EI), and body fat mass (FM) were measured longitudinally in 10 women pr econception; at 8-10, 24-26, and 34-36 wk of gestation; and 4-6 wk postpart um. Results: Compared with preconception values, individual RMRs increased from 456 to 3389 kJ/d by late pregnancy. DIT varied from -266 to 110 kJ/meal, T EE from -105 to 3421 kJ/d, AEE from -2301 to 2929 kJ/d, EI from -259 to 217 6 kJ/d, and FM from a 0.6-kg loss to a 10.6-kg gain. The only prepregnant f actor that predicted FM gain was RMR (r = 0.65, P < 0.05). Women with the l argest cumulative increase in RMR deposited the least FM (r = -0.64, P < 0. 05). Conclusions: Well-nourished women use different strategies to meet the ener gy demands of pregnancy, including reductions in DIT or AEE, increases in E I, and deposition of less FM than anticipated. The combination of strategie s used by individual women is not wholly predictable from prepregnant index es. The use of a single recommendation for increased energy intake in all p regnant women is not justified.