Danish cohort study published in the British Medical Journal last week that concluded that use of transdermal patches, vaginal rings & even subcutaneous implants increased relative risk of DVT while those who received levonorgestrel intrauterine contraception had equivalent risk compared to those women who did not use any hormonal therapy.Therefore I read w/interest a
But let's look deeper at the incidence of events per 10,000 exposure years. Last month's study quoted a baseline rate of 1-5 thrombotic events per 10,000 women-years, w/use of oral contraception increasing the absolute rate of thrombotic events to 3-9 per 10,000 women-years. As I noted, this still compared favorably w/baseline incidence of 5-20 thrombotic events during pregnancy over 10,000 women-years and 40-65 thrombotic events in the 12 weeks immediately post-partum.
This month's study claimed an incidence of 3.84 events per 10,000 exposure years, which compared favorably to last month's 1-5 events. Depending upon the type oral contraceptive used, rate of DVT increased to 6.63-8.68 events per 10,000 exposure years, again similar to last month's event rates.
However, the patch, vaginal ring and levonorgestrel implant increased event rates to 11.33, 10.93 & 5.09 events per 10,000 exposure years, which is still comparable to risk during pregnancy and much lower than during the 3 months immediately postpartum..
So while the relative risk may look amazingly elevated, this still compares favorably to the absolute risk of clots engendered during pregnancy & during the immediate postparum period. It's too bad that it's easier to get new/more attention w/overblown relative risk than the more truthful absolute risk. As always, when it comes to contraception, choose wisely! And don't forget that you still need to wear a barrier method to decrease the risk for sexually transmitted infections .