The pill doubles the risk of an ischemic stroke, the most common type caused by blood clots, even in women who are non-smokers or have a history of migraine or hypertension.
But the overall risk in these women still remains low. For every 100,000 women taking the pill, 8.5 will suffer a stroke, compared to 4.4 women who don't take the pill. In other words, there will be one additional case of stroke for every 24,000 women taking the pill, say researchers at the Loyola Medical Centre.
There's also a 40 per cent increased risk of stroke in women taking HRT (hormone replacement therapy), either estrogen alone or with progesterone. The risk increases with higher doses of HRT.
(Source: update to MedLink Neurology, September 2015; see: www.medlink.com)