From the article:
This large population study of more than 800 Swedish women who had VTEs and nearly 900 age-matched controls who took no hormones is helping answer those questions.
In this study, risk of having VTE [venous thromboembolism] was almost twofold higher (OR 1.72) in the women who took hormones than in those who took no hormones, which is similar to other studies, including the WHI. What’s more, women who took combined estrogen-progestogen therapy had nearly three times the VTE risk of those who took no hormones. Women who took estrogen only (because they had had hysterectomies and didn’t need a progestogen) had a much lower overall increase in their odds of VTE–a little less than one and half times higher (OR 1.31) compared with those who took no hormones. Women using combined estrogen-progestogen had a twofold higher risk of VTE than those taking estrogen only.
However, this study had good news about the way estrogen is delivered. There was no increased risk of VTE in this study for women who used transdermal estrogen (such as patches), either alone or in combination with a progestogen. And women who used vaginal estrogen alone to ease vaginal dryness and other symptoms of genitourinary syndrome of menopause (GSM) also had no increased risk of VTE. Many menopause experts don’t expect vaginal estrogen to raise the risk because absorption into the bloodstream is small and results in levels similar to those in postmenopausal women who use no hormones. But studies on this question have been rare, noted the authors, so this finding is a big help for decision making.
Whether the type of progestogen makes a difference in risk has also been an important question for women and clinicians, and there haven’t been many studies on this. Some imply that the VTE risk is higher with medroxyprogesterone acetate (the progestogen used in the WHI) than with norgestrel. But this study didn’t show any statistically significant difference in risk between the two synthetic progestins. What it did show was that having a uterus and taking both oral estrogen and a synthetic progestin increased the risk of VTE the most, particularly compared with estrogen only.