A ground-breaking study has found that mothers can go back to work months after the birth of their child without the baby's well-being suffering.
By assessing the total effect on a child of the mother going out to work, including factors outside the home, American academics claim to have produced the first full picture of the effect of maternal employment on child cognitive and social development.
Their conclusion will provide comfort for thousands of women who re-enter the job market within a year of giving birth.
"The good news is that we can see no adverse effects," said American academic Jane Waldfogel, a visiting professor at the London School of Economics.
"This research is unique because the question we have always asked in the past has been: 'If everything else remains constant, what is the effect of a mum going off to work?' But, of course, everything else doesn't stay constant, so it's an artificial way of looking at things.
"Family relationships, family income, the mental health of the mother all change when a mother is working and so what we did was to look at the full impact, taking all of these things into account."
In one of the most fraught areas of social policy and research, several studies over the past two decades have suggested that children do worse if their mothers work in the first year of their lives.
The new study, led by New York's Columbia University School of Social Work, was published by the Society for Research in Child Development.
It found that, while there were downsides to mothers taking work during their child's first year, there were also significant advantages - an increase in mothers' income and wellbeing, and a greater likelihood that children would attend high-quality childcare.
The net effect was neutral, the researchers said.
"The effect of the parenting itself is the key factor," said Professor Waldfogel.
"It is hugely important how sensitive you are to your child's needs. Even for women who have to work more than 30 hours a week, they can make things better for themselves, they just need to take a deep breath on the doorstep, dump all the office worries behind them and go in the door prepared to pay attention to all their children's cues.
"I'm delighted to have been able to disprove earlier studies.
"We just had to ask some different questions and this approach of looking at the whole picture is definitely the right question to be looking at.
"This is especially good news for US mothers, who typically go back to work after three months because of the lack of maternity leave."
Professor Waldfogel said that part-time work, up to 30 hours a week, was preferable to full-time employment.
The authors attribute their findings to the rich data used in the study, detailing parent-child interactions, income and childcare. They also used an analytic method that allowed them to calculate the total effect of maternal employment as it happens.
BACK ON THE JOB
Earlier studies about women returning to the workforce after having a baby have suggested that children did worse when their mothers went back to work.
Latest research: Higher income and improved wellbeing, with a greater prospect of children attending high-quality childcare tends to cancel out any downside.