Researchers at the University of Cambridge found having five or more children was associated with a 40 per cent increased risk of a serious heart attack in the next 30 years, compared with having just one or two children.
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.
Having three or four children was also associated with a modest increased risk of serious health implications, but the research found the most significant risk increases were seen with five or more children.
The findings also suggest the link between heart health and having children is independent of breastfeeding.
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. They found women who had a history of pregnancy loss, but no children had a 60 per cent increased risk of heart disease and a 45 per cent increased risk of heart failure in the following 30 years, compared with women who had one or two live births.
They said this was likely to reflect underlying health problems that increase the risk of pregnancy loss as well as heart disease and heart failure.
Previous research had been inconclusive on the relationship between heart health and the number of children a woman has given birth to. However, few studies have examined 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 in 2016.
She said: “Although you might think it’s unusual for women in their 40s 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.”
Dr Clare Oliver-Williams, who led the research 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.
“We don’t want to add to the stress people have in their everyday lives, but equip them with the knowledge to do something about it.”
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.”