Birth weight and mothers' adverse employment change.

Low birth weight has been linked at the aggregate level to unemployment rates and at the individual level to subjective distress. We hypothesize that maternal underemployment, including unemployment, involuntary part-time work, and low wage work predicts decreased birth weight. The relationship of birth weight to maternal employment changes during pregnancy was studied prospectively in 1,165 singleton first births in the National Longitudinal Survey of Youth data set. Controlling for other significant risk factors, women who shifted from adequate employment to underemployment had significantly lighter babies. Plausible mediators of this relationship were explored, including prenatal health care, gestational age, and mother's weight gain, with results varying by type of underemployment. Two interactions also suggested that underemployment reduced the beneficial effect of mother's weight gain on birth weight. These findings were partially replicated for low birth weight (< 2,500 grams), indicating the medical significance of the effect.