MedWire News: Users of the injectable contraceptive depot-medroxyprogesterone acetate (DMPA) are nearly four times more likely to develop venous thromboembolism (VTE) than nonusers of hormonal contraceptives, study findings indicate.
In contrast, the levonorgestrel (LNG)-releasing intrauterine device (IUD) is not associated with an increased VTE risk, report Frits Rosendaal (Leiden University Medical Center, The Netherlands) and colleagues.
"Oral contraceptive use is a well-established risk factor for the development of a first deep vein thrombosis (DVT), with risk estimates ranging from a 2- to 6-fold increased risk for users compared with nonusers," note the researchers.
Less information is available about the risks associated with nonoral contraceptives. Therefore, Rosendaal and team used data from the Multiple Environmental and Genetic Assessment study - a large case-control study on risk factors for VTE - to assess the risk for VTE among users of injectable DMPA, the LNG-releasing IUD, the contraceptive patch, and the contraceptive implant.
The team found that 20 (4.5%) of 446 women aged 18 to 50 years with a first episode of VTE were using injectable DMPA. This compared with 15 (1.3%) of 1146 controls with no history of VTE. Consequently, injectable DMPA was associated with a 3.6-fold increased risk for VTE compared with nonuse of hormonal contraceptives.
In contrast, the use of a LNG-releasing IUD device was not associated with an increased risk for VTE. Specifically, 3 (0.7%) patients with VTE were using an LNG-releasing IUD compared with 26 (2.3%) controls.
Adjustment for the potential confounders body mass index, positive family history of DVT, and smoking only marginally attenuated the risk estimates.
Of note, none of the patients or controls were using a contraceptive patch and only one patient was using a contraceptive implant, making it impossible to reliably estimate the risk for VTE associated with these contraceptive methods, say the team.
Rosendaal and co-authors conclude: "The risk for VTE was increased for injectable DMPA contraceptive users, while we were able to reliably exclude an increased risk associated with levonorgestrel IUD use"
"Therefore, the latter seems to be the safest option regarding the risk of venous thrombosis," they add.
The study findings are published in the journal Arteriosclerosis Thrombosis and Vascular Biology.
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