A new study has revealed that couples who intend to divide up childcare equally before their kid is born rarely achieve that balance once they become parents.

The study detailed that new parents believe that they spend more hours in childcare than they actually do. However, the study found that it was the woman who tended to be left with the lion’s share.

Both spouses overestimated their increased workload, but by widely varying amounts. The study found that compared to the parents' estimated hours of extra work each day, the time diaries showed women's workloads increased by two hours a day, while men's total working time each day increased by only about 40 minutes.

Professor Claire Kamp Dush, who co-authored the research said, “Women ended up shouldering a lot more of the work that comes with a new baby, even though both men and women thought they added the same amount of additional work”.

The study was conducted on dual-earner couples who adjust to becoming parents for the first time. The researchers followed 182 highly educated, dual-earning couples who had previously divided the housework equally.

Both spouses have jobs and reported that they continued to work even after the child is born. The couples were studied twice, once during the third trimester of pregnancy and then again when their babies were about 9 months old.

At both times, the spouses completed a detailed time diary for one workday and one non-workday separately. The couples reported working about 45 hours a week and spending a further 15 hours a week each doing housework.

However, nine months after the kids were born, the researchers interviewed the couples again. The couples reported that they spend about 90 hours a week. So both men and women felt like they had reduced their time at the office.

However, turns out, that the women spent on average 12 hours less looking after the kids than they thought they did (15 hours). Men did about 10 hours of physical child care, about two thirds of what they had reported.