In this case-control study that included 186 cases and 6134 controls, obesity was associated with a statistically significant 3-fold increased risk of cerebral venous thrombosis. Stratification by sex revealed that in women who used oral contraceptives, the risk was increased 30-fold. In contrast, we found no association in men or women who did not use oral contraceptives.
Despite those alarming relative risks increases the absolute odd is low however.
This paper is awsome: http://onlinelibrary.wiley.com/doi/10.1111/jth.12266/full
|Table 1. Overview of differential relative risks of a first VTE for various hormonal contraceptives and HRT|
Absolute risk (per 1000 person-years)*
HRT, hormone replacement therapy; VTE, venous thromboembolism. *Estimates of the absolute risk were obtained by multiplying the odds ratio with the baseline incidence of VTE of 0.39 per 1000 person-years for women aged 20–44 for hormonal contraceptives, and of 1.00 per 1000 person-years for women aged 45–54 for HRT . †Ethinylestradiol in the most commonly used dose of 30–40 mcg daily. ‡Upper limits of the 95% CIs (10.7 for noresthisterone and 7.1 for injectable depot medroxyprogesterone) do not exclude a strong risk increase. §Inconsistent results from no increased to an increased risk of VTE as compared to oral contraceptives containing norgestimate; no data available of patch users vs. non-users. ¶Upper limit of the 95% CI (3.4) does not exclude a risk increase. **Data from SAE reporting in clinical outcome studies. Wide confidence intervals do not exclude a modest or strong risk increase. ††Upper limit of the 95% CI (1.7) does not exclude a modest risk increase.
Strong risk increase (odds ratio 5–8) [7, 105-107]
Oral progestagen only, high dose (5–30 mg)
Moderate risk increase (odds ratio 2–5) [7, 108]
Injectable depot medroxyprogesterone‡
No risk increase [12, 109, 110]
Levonorgestrel releasing IUD
Progestagen only, low-dose norethisteron 350 μg or levonorgestrel 30 μg
Progestagen only, low-dose desogestrel 75 μg¶
Etonogestrel subcutaneous implant
Vaginal ring (ethinylestradiol/etonogestrel)
Moderate risk increase (OR 1.5–3.0) [11, 112]
Oral combined estrogen/progestagen pills
Oral estrogen only
No risk increase [11, 112]
Transdermal (combined estrogen/progestagen and estrogen only) ††