Having more bundles of joy can actually be bad for your health. PICTURE: Supplied

Do you have 2 or more children? You're at risk of heart disease because they are so expensive to look after

If you have more than two children you're at risk of heart disease, new research suggests. And it doesn't matter whether you're a man or a woman the chances are the same, experts claim. One child offers protection to parents, but any more than this increases the financial pressure on them to provide.

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This burden causes extra stress to fathers, while hormonal changes from multiple pregnancies affect women, a study found. A study of 500,000 people found a 'significant' relationship between number of children and risk of coronary heart disease the world's leading killer.

The Chinese researchers noted that having two children was the cut-off point with those who were parents to just one at less risk.

This provided evidence that pregnancy leads to alterations that change the body's reaction to additional cardiovascular risk factors. But the findings, which were published in the journal Circulation, also gave a socioeconomic explanation.

'The striking thing was that the Chinese study showed the same association for women and men,' said Professor Regitz-Zagrosek, chairperson of the European Society of Cardiology.

'Number of children should be considered a new factor that may influence the risk for some cardiovascular diseases for women and men and included in research databases to be further investigated as a health indicator. Having one child is protective because parents have social support in older age. 'But if they have a large number of children this benefit goes away because it increases the economic and social pressure on the parents.'

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While another study found that experiencing multiple pregnancies increases a woman's risk of developing an irregular heartbeat later in life.

Known as atrial fibrillation, the condition can lead to blood clots, stroke and heart failure.

Researchers from McMaster University, Canada, and Brigham and Women's Hospital, Boston, assessed 34,639 participants. They discovered women who had been through four or more pregnancies were approximately 50 per cent more likely to develop the condition.

Also published in Circulation, the researchers speculated that exposure to hormones during pregnancy could explain the link. But they were keen to not discourage women from having children, instead highlighting the need for further research.