The prevalence and severity of chronic energy deficiency (CED) among women of reproductive age as well as its consequences on the newborn and the mother were assessed in a longitudinal study. More than 40% of the mothers had a Body Mass Index (BMI) less than 18.5 before pregnancy, a level below which CED is considered to exist. Weight gain during pregnancy was low, on average 6.6 kg. Taking the difference between 4 week postpartum weight and pre-pregnant weight as net weight gain during pregnancy, mothers with a BMI less than 18.5 before pregnancy gained weight while those with a higher BMI lost weight. This observation suggests that the partitioning of energy to the fetus and the mother depends on the energy reserves of the mother before pregnancy. The functional significance of BMI as an indicator of CED is illustrated by its relation with birth weight. Similarly, 4 week postpartum, weight and BMI were predictive for the weight changes in the mother in the first 12 months after delivery. The groups with the lowest values gained weight, while the heaviest mothers lost weight. In view of the negative effects of CED among women of reproductive age on the infant and the mother, maternal undernutrition should receive the same attention as malnutrition among preschool children.