The findings, published in the journal Menopause, add to evidence that skin patches can be a safer alternative to pills for women who want to treat their bothersome menopause symptoms with hormone replacement therapy (HRT).
The number of women using HRT plummeted in 2002 after a large U.S. clinical trial found that women on estrogen-plus-progesterone pills had higher risks of blood clots, heart attack, stroke and breast cancer than placebo users did.
Up to that point, HRT had been prescribed to prevent heart disease and osteoporosis. Experts now advise against that.
However, hormone therapy remains the most effective way to ease menopausal hot flashes, so some women with severe symptoms still opt for it. Because of the risks, experts say women should use HRT at the lowest dose and for the shortest time possible.
There is growing evidence, though, that low-dose patches may not carry all the risks that pills do.
Some studies have found that, unlike pills, patches may not raise women's risk of a first-time venous thromboembolism (VTE), which refers to blood clots either in the leg veins or the lungs.
And a large UK study earlier this year found that women who used low-dose patches for hormone therapy had no greater risk of stroke than women not on HRT. Those on hormone pills or high-dose patches, however, did have a higher stroke risk than non-users.
Most strokes are caused by clots that disrupt blood flow to the brain.
For the new study, French researchers looked at hormone therapy and the risk of repeat VTEs among women who had already been treated for one.
Of the 1,023 women they followed, 103 started using hormone patches for menopausal symptoms after stopping their VTE treatment -- which usually involves several months on anti-clotting drugs. Another 10 women used oral HRT, and the rest did not use any hormone replacement.
Over an average of 6.5 years, 77 women -- or 1 percent per year -- suffered a repeat blood clot. For women using hormone patches, the risk was no greater than it was for women not on
Of the 103 women who used the patches, six had a repeat blood clot. In contrast, two of the 10 who used hormone pills had a repeat clot. When the researchers weighed other factors, like the women's age and weight, those on pills showed a six-fold greater risk of a repeat blood clot than women who did not use hormone therapy.
The findings suggest that even for women at high risk of VTE, hormone patches may not further that risk, lead researcher Valerie Olie, of the French national research institute INSERM, told Reuters Health by e-mail.