Adolescents with Adequate Birth Weight Newborns Diminish Energy Expenditure and Cease Growth

Maternal energy requirements increase during pregnancy but the magnitude of this increment is unknown among adolescents. We determined the effects of maternal age and weight status on adjustments in gestational weight gain, resting energy expenditure (REE), and growth among adolescents. Weight, and growth rates of pregnant adolescents (PA) < or =17 y during late pregnancy were compared with changes in nonpregnant adolescents (NPA) over a 5-mo period. REE was also measured monthly in the PA group. Paired t-tests and general linear models for repeated measures were used for the analysis; height was included as a confounding variable. Weight, height, and BMI of the PA and NPA women did not differ at baseline. During the follow-up period, NPA grew 0.94 +/- 30 cm; growth rate was greater in adolescents < or =14 y of age (P < 0.001) than in the older subjects. No growth occurred in the PA group. REE tended to increase linearly between 20 and 36 wk of gestation (P = 0.164); the net change in women >14 y (25%) tended (P = 0.164) to be greater than that of younger adolescents (7%). The mean increment of REE from wk 20 to wk 36 was 230 +/- 30 kcal/d (962 +/- 126 kJ/d) and the smallest increase occurred in women with BMI <20 (P = 0.010). Women with BMI <20 had a decrease in REE/kg that was greater than that of normal weight (BMI 20-25) or overweight (BMI > or =25) women (within subject, P = 0.010; between subject, P = 0.001). In conclusion, PA appear to adjust their resting energy needs by ceasing growth.