Electronic Thesis and Dissertation Repository


Master of Science


Epidemiology and Biostatistics


Sarma, S.

2nd Supervisor

Campbell, M. K.

Joint Supervisor


Background: Childhood overweight and obesity is a major public health issue, with approximately 1 in 3 children classified as overweight or obese in Canada. Research suggests that maternal employment during childhood may be associated with later overweight and obesity risk, but it is not known whether employment during infancy and toddlerhood has a similar effect on weight status. Mechanisms such as reduced breastfeeding and use of informal child care have been proposed in the literature but not been formally tested among infants and toddlers. It is important to identify possible mechanisms that could explain the association with overweight and obesity risk in order to identify strategies for prevention.

Objectives: The objective of this study was to investigate, in a Canadian sample, whether maternal employment during infancy and toddlerhood is associated with a higher risk of childhood overweight/obesity. A secondary objective was to determine whether breastfeeding and type of child care mediate this association.

Methods: Data were obtained from the National Longitudinal Survey of Children and Youth, a nationally representative survey of Canadian children conducted by Statistics Canada. A cohort of children ages 0-2 years in Cycle 3 (1998/1999) with follow-up information in Cycle 7 (2006/2007) was used for the analysis. Modified Poisson regression was used to examine whether maternal employment (no work, part-time, full-time) during infancy and toddlerhood was associated with overweight/ obesity risk at ages 8-10 years. A mediation analysis determined whether breastfeeding (0-4 weeks, 5 weeks to 6 months, >6 months) and child care (no child care, informal care, formal care) mediated the association. Analyses were stratified by gender and adjusted for known confounders.

Results: Maternal employment in infancy and toddlerhood was not significantly associated with overweight/obesity in girls at ages 8 to 10 years. In boys, adjusted analyses indicated an increased risk (RR=1.38, 95% CI=1.04-1.84) of overweight/obesity for full-time maternal employment in infancy and toddlerhood. The association was non-significant in a sensitivity analysis. Breastfeeding for 4 weeks or less was associated with an increased overweight/obesity risk in boys compared to breastfeeding for over 6 months. This study contributes evidence in support of ensuring that all mothers receive the opportunity for maternity leaves for a minimum of 6 months, allowing adequate breastfeeding support.

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