Changes in maternal upper arm fat stores are predictors of variation in infant birth weight.

The relationship between changes in maternal subcutaneous fat and infant birth weight was studied in 608 low income women. A loss of upper arm fat area (> 6.4 cm2), measured from 28 wk gestation to 4-6 wk postpartum, was associated with greater birth weight (+144 g, P < 0.01). However, when pregravid weight was low (< 25th percentile for age), a loss of upper arm fat area was associated with a birth weight lower by more than 300 g than that for women with higher pregravid weights who also lost fat, indicating that maternal stores among those with low weight may have been relatively depleted. Continued gains in upper arm fat area (> 5 cm2) from 28 wk gestation to the postpartum period was also associated with a lower birth weight (-123 g, P < 0.02). The mothers who gained upper arm fat late in pregnancy or continued to accrue fat in the postpartum period had the largest gestational weight gains, bore infants who were smaller, and retained the most weight postpartum. Thus, change in upper arm fat is a significant predictor of variation in infant birth weight.

Maternal weight gain, diet and infant birth weight: correlations during adolescent pregnancy.

Inadequate weight gain during pregnancy is an important risk factor for low birth weight (LBW), but the contribution of diet to weight gain is uncertain. Pregnancy weight gains were examined at 4-week intervals from 12 to 36 weeks' gestation, as well as total gain for gestation, in a cohort of over 2000 young pregnant women, aged less than or equal to 18 at entry to prenatal care. The effect of diet was studied in a 15% random sample of the cohort, using a 24-hour dietary recall obtained at entry to prenatal care (averaging 17 weeks' gestation). As early as 16 weeks' gestation, gains below the lower limit of a clinical standard were associated with a decrement in birth weight at delivery of more than -85 g (p less than 0.01), and after 24 weeks of approximately -180 g (p less than 0.001). After adjusting for potential confounding variables, teenagers who went on to develop inadequate total weight gain for gestation had consumed 1878 kcal vs 2232 for teenagers with adequate total gain (p less than 0.05). There were significant deficits in protein (p less than 0.05) and carbohydrate intake (p less than 0.05) associated with inadequate gain. However, there was no direct effect of nutrient intake on birth weight, LBW, or preterm delivery. This suggests that the relationship between nutrient intake during pregnancy and birth weight may be indirect and moderated by weight gain during pregnancy.