Women who have given birth have a higher chance of developing heart disease and strokes than those who are childless, a new study says.

Previous studies have shown that women usually show changes in vascular properties, blood volume and heart rates during pregnancy. However, the impact of pregnancy on subsequent heart disease has been debated. In the new study, a team from the Huazhong University of Science and Technology in China, reviewed 10 studies. It involved nearly three million women worldwide, with more than 150,000 diagnosed with heart disease or strokes during the following six to 52 years.

The findings, published in the European Society of Cardiology journal, showed that giving birth has a 14 per cent higher risk of heart disease and strokes. In addition, there was a significant association between the number of pregnancies and the risk of cardiovascular disease.

Women had a four per cent increase in the incidence of cardiovascular disease each time they gave birth, regardless of weight, diabetes, high blood pressure, smoking and income. Each delivery increased the risk of coronary heart disease by five per cent and strokes by three per cent, the researchers said.

According to Wang Dongming, lead researcher from the varsity, pregnancy could cause inflammation within the body and accumulation of fat tissue around the abdomen, in the blood and arteries. These changes may have a permanent impact on the cardiovascular system, leading to an increased risk of heart disease and stroke. However, he said women could do a lot to prevent cardiovascular disease. The researchers suggested quitting smoking, doing more exercises, a healthy diet, and controlling weight to improve future health.