Every ten-point increase in diastolic blood pressure raises the danger by almost a fifth, a study found.

London - Women who have high blood pressure before becoming pregnant could be at greater risk of miscarriage.

Every ten-point increase in diastolic blood pressure raises the danger by almost a fifth, a study found.

US researchers looked at more than 1 200 women who had already suffered one or two pregnancy losses and were trying again for a baby.

They found a link between their blood pressure and chances of a miscarriage - even if women did not have what is classed as medically high blood pressure.

It is unclear why high blood pressure before pregnancy may cause miscarriage, or why it raises the risk of giving birth to premature underweight babies, which was already known.

It may be that women with pre-existing high blood pressure make less of a special protective layer inside their blood vessels.