Despite increases in average family incomes, child poverty has edged up over the past three decades. Today, more than one in ten OECD children lives in poverty. Beyond poverty, infant mortality rates are falling and the proportion of children born weighing less than 2.5 kilograms is on the rise. Moreover, inequalities in health, education and material well-being raise concerns about children being left behind in a number of OECD countries. More mothers with young children are in paid work than in the past. There is a longrunning debate on possible negative effects of maternal employment on child development. For the first time, this chapter presents results from panel data studies on child outcomes in different OECD countries to help answer the question: what is a good moment for mothers to go back to paid work? The evidence suggests that a return to paid work by mothers within six months after childbirth may have negative effects on child outcomes, but the effects are small and, in certain circumstances, balanced by positive effects related to earning extra family income. The evidence in the literature on the effects of parental leave policies on child well-being is mixed, and the cross-national analysis in this chapter finds no evidence of significant positive or negative effects of parental leave reform on child well-being either.