Maternal growth during pregnancy and the competition for nutrients.

The influence of maternal growth in knee height during pregnancy on birth weight, gestation, and maternal body composition was examined in 318 teenagers (144 growing, 174 nongrowing) and 276 mature women from the Camden Study. Body-composition differences associated with maternal growth did not arise until after 28 wk gestation, when growing gravidas continued to accrue fat, had larger gestational gains, and retained more of their gestational weight gain postpartum. Nevertheless, still-growing young mothers had infants with lower birth weight, particularly when the mother continued to accrue higher amounts of fat on the arm or back (subscapular site) late in gestation. Thus, despite an apparently sufficient weight gain and the accumulation of abundant stores during pregnancy, young still-growing women appeared not to mobilize fat reserves late in pregnancy to enhance fetal growth, apparently reserving them instead for their own continued development.