Early-years and childcare workers quit their jobs when they become parents because of poor pay and guilt about leaving their children with other carers, a report shows.
It reveals that although they are happy to care for other people's children, some staff believe that their own offspring would be best brought up at home.
The report, from Manchester Business School, says most nursery nurses "can earn the same working in Topshop or Asda, without the responsibility". This meant there were fewer early-years staff between 25 and 35 than in older age groups.
Researchers from the European Work and Employment Research Centre interviewed 120 workers and managers in 35 private and public nurseries in north-west England.
They found that low pay influenced how the work was valued. Poor earnings encouraged society to attach low value to a job, which in turn damaged recruitment and retention.
"Nursery workers are more likely to be poorly paid than social care workers, in spite of having two years' training and the same level of qualification," it said.
The report, funded by the European Social Fund, revealed that nursery nurses and other child-care staff working for private providers could not afford to place their children in nurseries where they worked, even when offered discounts by owners.
Researchers Mark Smith, Sirin Sung, Marilyn Carroll and Gwen Oliver said the findings also highlighted tensions between looking after other people's children and their own.
"Although childcare workers are trained to provide professional childcare services, they appeared to construct these services negatively, as 'leaving' one's children, rather than positively 'giving' them an opportunity," they said.
"This perspective, combined with practical difficulties, may further encourage childcare workers to leave in order to provide the 'ideal, home-based' care for their own children.
"Thus the beliefs and expectations about motherhood may have implications for retention and loss of staff in formal childcare and early education services.
"Parents may prefer not to pay for their child to be cared for while being paid to look after other people's children, but it is also likely that childcare workers simply do not earn enough to pay for formal childcare."