The more children a woman has, the greater her risk of heart attack, stroke and heart failure, research has shown.
Researchers at the University of Cambridge found having five or more children is associated with a 40% 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% increased risk of heart disease - the major cause of heart attacks - as well as a 25% increased risk of stroke and a 17% 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 that the most significant risk increases were seen with five or more children.
The findings also suggest that 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.
The University of North Carolina was also involved in the research.
They found women who had a history of pregnancy loss but no children had a 60% increased risk of heart disease and a 45% increased risk of heart failure in the following 30 years, compared with women who had one or two live births.
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 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.
"The number of children a woman has had is an easy sign of whether a woman is at greater risk.
"We all know it's hard to take care of your health when you have children, but hopefully this research can help show how important it is and, perhaps, having children can provide some extra motivation."
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.
"Research like this can help us understand who is at the highest risk of heart attacks and it's vital we continue to fund more life-saving research into heart disease to keep families together."