Oestrogen may be an added risk factor for certain women who contract Covid-19, a new study suggests.
Researchers found infected women who are pregnant or take oestrogen for birth control or as part of hormone-replacement therapy (HRT) may be more likely to develop blood clots.
The new study, which was published in the Journal of Endocrinology, says contraceptive pills contain oestrogen that can narrow blood vessels and increase the chance of blood clots. Those who are pregnant or on HRT face the same danger.
If these women become infected with Covid-19, their risks increase even further and they may need to stop using their oestrogen medication or undergo anticoagulation therapy, such as taking blood-thinning medication.
Evidence suggests the coronavirus can cause blood clots to form even in previously healthy people, says Dr Daniel Spratt, the study's corresponding author.
He adds that oestrogen fuels potentially deadly deep-vein thrombosis in some mothers-to-be, as well as those on the pill or taking HRT. The blockages usually start in the legs but can move upwards and trigger a heart attack or stroke.
Oral contraceptives are known to carry a small risk of this condition and, Dr Spratt says, this may be exacerbated by the coronavirus.