More mothers are in paid work because grandparents are helping with childcare, a study has found.
It reveals that grandparents' involvement in looking after their grandchildren means that around 25% more mothers are able to go to work.
The Birmingham University research, published in the Journal of Social Policy, used data from the Millennium Cohort Study to analyse the main source of childcare for thousands of children at the age of five, and whether their mothers worked.
It found that grandparents were the first named source of after-school and weekend care for 36% of children of lone mothers and 32% of those whose mothers had a partner.
Overall, 56% of mothers involved in the study were working, and this would have been 26% lower if grandparents had not been looking after children, the study concludes.
Author Shireen Kanji told the Press Association: "Grandparent care is raising participation in paid work for mothers at all qualification levels.
"It seems to have less of an impact on mothers with high levels of qualifications, but they are also much more likely to be in work.
"For those with no qualifications, or low levels of qualifications, it can literally almost make the difference between whether they can work or not.
"The contribution of unpaid work, often performed by women, is often unrecognised.
"Grandparents are having a large causal effect on mothers' participation in paid work in the UK but grandparents themselves are under pressure to extend their paid working lives as a result of recent changes to the state pension age."
Caroline Abrahams, charity director at Age UK, said: "With childcare costs rising much faster than wages, it inevitably means that more grandparents are getting involved in day-to-day childcare activities as families look to save money.
"Our latest research shows that two-fifths of all grandparents in the UK have provided some form of regular childcare for their grandchildren.
"Without this army of grannannies, many parents would struggle to keep working which is why it's so important that the Government and employers do more to make sure that flexible working is the norm, not the exception."