WASHINGTON - POSTMENOPAUSAL women who have breastfed a child have a lower risk of heart attacks, stroke and cardiovascular disease, a study released on Tuesday found.

The study of 139,681 postmenopausal women found that those participants who breastfed for at least one month had lower blood pressure, better cholesterol and less frequent diabetes.

They are all known factors for cardiovascular risk, according to the study in the May issue of 'Obstetrics and Gynecology.'

And the longer mothers breastfed, the more apparent the cardiovascular benefit, the study also found.

Women who breastfed for more than a full year had their cardiovascular risk reduced by 10 per cent, said lead researcher Eleanor Bimla Schwartz, a professor of medicine at the University of Pittsburgh Schools of the Health Sciences.

'The longer a mother nurses her baby, the better for both of them,' Ms Schwarz said.

'Our study provides another good reason for workplace policies to encourage women to breastfeed their infants.

'Heart disease is the leading cause of death for women, so it's vitally important for us to know what we can do to protect ourselves,' she added.

'We have known for years that breastfeeding is important for babies' health; we now know that it is important for mothers' health as well,' Ms Schwarz said.

The study was carried out under the US federal government's Women's Health Initiative study on chronic disease launched in 2004, and funded by the National Institutes of Health.