The study by academics at the University of Cambridge showed the biggest risks were to mothers with five or more children, but increased with each successive child.

Pregnancy and childbirth each put significant strain on the heart, the researchers suggest, and this is in addition to the stress and demands of raising a larger family which leaves less time for self-care.

Having five or more children was also associated with a 30 per cent increased risk of heart disease – the major cause of heart attacks – as well as a 25 per cent increased risk of stroke and a 17 per cent increase in the risk of heart failure compared with one or two children.

The authors said they hoped the findings would help provide "extra motivation" for parents of large families to take extra steps to protect their heart in other ways, such as diet and exercise.

Previous studies have suggested that breastfeeding may help protect the heart, but this research found it did not completely offset the extra risk of having more children.

The study, which is being presented at the British Cardiovascular Society Conference in Manchester, saw the team study data from more than 8,000 white and African-American women from the United States who were aged 45 to 64.

It also looked at women who had a history of pregnancy loss, through miscarriage or other factors, and found these women had a 60 per cent higher risk of heart disease than women who had one or two children.

They said this is likely to reflect underlying health problems that increase the risk of pregnancy loss as well as heart disease and heart failure.

Previous research has been inconclusive on the relationship between heart health and the number of children a woman has given birth to, with few examining multiple outcomes such as heart disease and heart attacks.

Jules Conjoice, 48, from Letterston in Pembrokeshire, has four children and had a heart attack on New Year’s Eve 2016.

She said: “Although you might think it’s unusual for women in their forties to have a heart attack, I’m proof that it can happen to any of us. It’s frightening how many people have heart attacks and don’t survive.

“As a busy mother I’m always putting my family first, and looking after my health can take a back seat sometimes.

“I hope research like this brings it home to busy mothers and fathers that it’s important to look after themselves as much as they care for their families.”

Dr Clare Oliver-Williams, who led the study at the University of Cambridge, said: “The aim of my research is not to scare women but to bring to their attention as early as possible whether they might be at increased risk of heart attacks."

“We know that pregnancy and childbirth put a tremendous strain on the heart, and raising children can be very stressful, too.

She added that the number of children a woman has "is an easy sign" of increased risk, and hopefully this research will provide "extra motivation" to keep healthy.

Professor Jeremy Pearson, associate medical director at the British Heart Foundation, which funded the study, said: “Research like this reminds us that – regardless of the stereotype of the overweight, middle-aged man having a heart attack – heart disease strikes men and women alike.

“As the major cause of heart attacks and strokes, heart disease cruelly tears families apart.

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