Hormone replacement therapy increases the risk of stroke by almost a third, a review of clinical trials says.
HRT has been linked to health problems
Concerns about the safety of long-term HRT use have grown after a series of studies linked it with a higher risk of breast cancer, heart attack and stroke.
Researchers at the University of Nottingham reviewed the results of 28 trials involving almost 40,000 patients.
They concluded that HRT increased the risk of stroke by 29%.
The UK's Royal College of Obstetricians and Gynaecologists has advised that HRT should only be used in the short term to relieve menopausal symptoms.
HRT has in some cases been prescribed to women to reduce the risk of osteoporosis - a measure which is now discouraged.
The latest review found HRT was associated with a particularly sharp increase in the risk of ischaemic stroke, which is caused by an insufficient blood supply to the brain.
The severity of the stroke also increased with HRT use.
The researchers, led by Professor Philip Bath, said it was unclear why HRT should increase the risk of stroke
and its severity when some studies had suggested it might have a protective
The review will raise further concerns among women seeking treatment for symptoms of the menopause, which can include debilitating hot flushes, insomnia,
headaches and irritability.
The number of prescriptions for HRT has fallen as more trials have emerged highlighting possible dangers.
A Department of Health spokeswoman stressed the importance of using the lowest possible dose of HRT for the shortest possible time.