Pregnancy and labour put strain on the heart, while children are stressful and stop mothers looking after themselves properly, the researchers suggest. Picture: AP

London - Most parents will agree that children raise their stress levels. Now it appears that having more than two can significantly damage a mother’s health.

The more children a woman has, the greater the risk of heart attack, stroke and heart failure, according to a study led by Cambridge University.

Those with five or more children were 40 percent more likely to have a serious heart attack in the next 30 years compared to women with one or two children.

Pregnancy and labour put strain on the heart, while children are stressful and stop mothers looking after themselves properly, the researchers suggest.

Cambridge’s Dr Clare Oliver-Williams, who led the research, said: "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."

Scientists from Cambridge and North Carolina studied data from more than 8 000 women from the United States, who were aged between 45 and 64.

Having five or more children was also associated with a 30 percent increased risk of heart disease, the major cause of heart attacks. They were a quarter (25 percent) more likely to have a stroke and almost a sixth (17 percent) more likely to have heart failure than mothers of one or two.

The researchers found women who had between three and four children were more likely to have serious health implications, but the most significant increase was in those with five or more.

Women who have had miscarriages were found to have a 60 percent greater risk of heart disease and were 45 percent more likely to go on to have heart failure.

But this is likely to be the result of underlying health problems that increase the chances of pregnancy loss, the researchers said.

Unlike previous studies which suggested breastfeeding helped protect against cardiovascular disease, it found this did not have an impact on the heart health of mothers.