Evidence from maternity leave expansions of the impact of maternal care on early child development

"We study the impact of maternal care on early child development using an expansion in Canadian maternity leave entitlements. Following the leave expansion, mothers who took leave spent between 48 and 58 percent more time not working in the first year of their children's lives. We find that this extra maternal care primarily crowded out home-based care by unlicensed non-relatives, and replaced mostly full-time work. However, the estimates suggest a weak impact of the increase in maternal care on indicators of child development. Measures of family environment and motor-social development showed changes very close to zero. Some improvements in temperament were observed but occurred both for treated and untreated children"--National Bureau of Economic Research web site