Is hormonal contraception and hormone replacement therapy feasible following an episode of pulmonary thromboembolism or deep vein thrombosis?
Shannon Bates: I think there are two situations where you may consider using hormonal contraception following an episode of venous thromboembolism. The first is if the woman has elected to stay on anticoagulants. For the longest time, there has been controversy as to whether it has been safe to maintain women on, say, oral contraceptive pills once they have had a venous thromboembolic event if they are going be staying on anticoagulants for an extended period of time. The International Society on Thrombosis and Hemostasis (ISTH) a few years ago released a subcommittee consensus statement saying that it was probably safe as long as you remember to stop the hormonal therapy before you stop the anticoagulants. The problem is that there have been some guidelines from the World Health Organization that suggested it was not safe to be using hormonal therapy for contraception even in women who were receiving adequate anticoagulant therapy. What has helped clarify the situation is the recent substudy published by Martinelli et al from the EINSTEIN VTE studies that have shown that in women in those studies who were receiving either rivaroxaban or warfarin and receiving either combined hormonal therapy or progesterone-only therapy, their risk of recurrence on anticoagulant therapy was not any higher than in women who were not receiving hormonal therapy. So that is the first lesson: as long as women are receiving adequate anticoagulant therapy and are well managed, they can probably be maintained on hormonal therapy if there is a good indication for that.
The second situation would be women who are not on anticoagulant therapy and want some type of hormonal contraception. Then your options are limited. There are basically two types of hormonal therapy that have not been clearly associated with an increased risk of venous thromboembolism. The first is the levonorgestrel intrauterine device (IUD), or Mirena IUD (the brand name in North America). The data suggest that there is no increased risk of venous thromboembolism with that device. And a 95% confidence interval around their risk estimate is quite small. So I think people can feel confident that they are not exposing their patients to undue risk.
The other hormonotherapy that might be safe in these women, but the data is not as strong, is the progesterone-only pills, the mini-pill. The point estimate from studies suggest that it is not associated with an increased risk of venous thromboembolism but you are not able to say this for sure, because the 95% confidence intervals around their risk estimate are still on the broad side.