Previous research indicates that the duration and intensity (e.g., hours worked) of maternal employment is positively associated with children’s body mass index (BMI; a measure of weight-for-height) and overweight, particularly among families with more educated mothers (Anderson, 2012). Fewer studies have considered the timing of maternal employment. A growing body of evidence suggesting that the influence of mothers’ work on children’s BMI may be stronger during certain periods in a child’s lifetime, particularly middle childhood and adolescence (Ruhm, 2008; Scholder , 2008). Older children may have more independence than younger children; thus, maternal employment during middle childhood or adolescence may precipitate poorer food choices and more sedentary activity. However, the mechanisms are not well understood.

 This study investigates whether mothers’ employment patterns across a child’s lifetime are associated with their children’s body mass index (BMI) and overweight at adolescence. We also examine potential mechanisms that may explain these relationships, and whether relationships vary by maternal education. We use two comprehensive, longitudinal datasets: the National Longitudinal Survey of Youth (NLSY) and the Children of the NLSY (N = 4,087) and the NICHD’s Study of Early Child Care and Youth Development (SECCYD; N = 1,364). Using multiple imputation, we conduct multivariate regression analyses predicting children’s BMI z-scores (a standardized measure of BMI by age and gender), overweight (BMI>=85th percentile for height and weight by age and gender), and obesity (BMI>=95th percentile) at adolescence from their mothers’ work hours at different developmental periods: prenatal, the first year of life, the second year, preschool (ages 3-5), middle childhood (ages 6-10), and adolescence (ages 11-13/14 or 15). A wealth of child and family characteristics are controlled.

 Results indicate that across both datasets, mothers’ average weekly work hours are associated with higher measures of standardized BMI and greater odds of being overweight or obese at adolescence. As shown in Table 1, maternal work hours during years 6-10 are associated with higher measures of BMI and obesity at age adolescence in both datasets. Maternal employment during other developmental periods is largely unrelated to child BMI at adolescence. In Table 2, analyses with the NLSY indicate that these associations are only apparent among adolescents with high-educated mothers. Also among these more advantaged children, mothers’ work hours during adolescence are associated with lower odds of being overweight at age 13 or 14. Mediation analyses using the SECCYD, which contains a relatively advantaged sample, suggest that the number of hours of sleep per night that children received at 3rd grade mediates about 15% of the effect between maternal work hours from ages 6-10 and weight outcomes at age 15; time spent watching TV, physical activity measures, or food consumption do not appear to mediate this relationship.

 Results support previous studies that maternal employment is positively associated with children’s BMI. We find that this association may be limited to middle or later childhood years. Children’s sleep may be one potential target for intervention. Given the serious consequences of obesity, this issue has important implications for child well-being and public policy.