PARIS, March 11, 2009 (AFP) - Migraines in pregnancy could be a clue that a woman is at risk of a stroke, heart disease and blood clots, according to a study published online Wednesday by the British Medical Journal (BMJ).

Researchers led by Cheryl Bushnell, a neurologist at Wake Forest University in Winston-Salem, North Carolina, trawled through a database of 18 million records of US patients who had been discharged from hospital from 2000-2003.

They found nearly 44,000 cases of pregnant women who had been admitted with a migraine.

Within this group, there was a strong association with treatment for stroke, heart attack, high blood pressure and the dangerous condition in pregnancy known as pre-eclampsia.

Still unclear is whether the migraine came before the cardio-vascular condition or after it, so more research is needed, the paper says.