Findings from U.S. research which tracked more than 1,000 infants from birth to age seven reignited the debate over the impact on young children whose mothers work long hours.
Researchers found that babies brought up by mothers who resumed full-time work before they turned one tended to do worse in ability tests - a disadvantage that persisted into primary school.
But those negative effects were counterbalanced when the researchers took into account the benefits of having a job, such as higher earnings, it was claimed.
Working mothers were also more likely to use good quality childcare because they could shop around for the best providers, the study found.
And, controversially, it said they showed greater 'maternal sensitivity' - or responsiveness towards their children - than stay-at-home mothers.
These 'indirect' benefits aided children's development, balancing the downsides of full-time work, the researchers said.
The 'overall effect' of mothers working during their child's first year was ' neutral', according to researchers at Columbia University.
But the study also found that the positive effects of working depended on mothers finding high-quality childcare and being skilled parents while not at work.
And while mothers in full-time work did no harm to their children, youngsters' prospects were significantly improved if mothers worked part-time - up to 30 hours a week - during the first year instead. 'Our results point to some clear advantages for children whose mothers worked parttime rather than full-time in the first year of their life,' the research said.
The weight of the evidence suggests that having a mother who works part-time in the first year does lead to better outcomes, on average, than having a mother who works full-time in the first year.'
See more
