WOMEN age by up to two years for each baby they have, say researchers.

Cell changes in pregnancy may have a lasting negative impact, they found.

Each child could slash the mum’s life expectancy and make poor health more likely.

The US researchers studied cells taken from 821 women aged 20 to 22 who had up to five kids.

Those with most offspring had DNA with shorter protective telomeres and more of another marker that both indicate genetic ageing.

The changes are linked to a shorter lifespan and ill health.

Analysis found that each birth increased a mother’s cellular age by six months to two years.

Yet her cells looked temporarily younger during pregnancy and she may have a glow that makes her appear more youthful.

Study leader Calen Ryan, from Northwestern University in Chicago, said he was surprised by the scale of the ageing.

He added: “The markers independently predict mortality and both appeared older in women who have had more pregnancies.

“Even accounting for other factors that affect cell ageing, pregnancy numbers still came top.”

His colleague Prof Christopher Kuzawa wants research to see if the changes persist in older age.