Prescribing oral contraceptives in obese women is very dangerous

"The study included 186 cases and 6134 controls. Cases were younger (median age, 40 vs 48 years), more often female (133 [71.5%] vs 3220 [52.5%]), more often used oral contraceptives (97 [72.9%] vs 758 [23.5%] of women), and more frequently had a history of cancer (17 [9.1%] vs 235 [3.8%]) compared with controls. Obesity (BMI ≥30) was associated with an increased risk of CVT (adjusted odds ratio [OR], 2.63; 95% CI, 1.53-4.54). Stratification by sex revealed a strong association between CVT and obesity in women (adjusted OR, 3.50; 95% CI, 2.00-6.14) but not in men (adjusted OR, 1.16; 95% CI, 0.25-5.30). Further stratification revealed that, in women who used oral contraceptives, overweight and obesity were associated with an increased risk of CVT in a dose-dependent manner (BMI 25.0-29.9: adjusted OR, 11.87; 95% CI, 5.94-23.74; BMI ≥30: adjusted OR, 29.26; 95% CI, 13.47-63.60). No association was found in women who did not use oral contraceptives."
http://archneur.jamanetwork.com/article.aspx?articleid=2500277

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

Hormonal contraceptives

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 [3]. †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]


Ethinylestradiol†/desogestrel

2.8 (2.1–3.9)


Ethinylestradiol†/cyproterone

2.7 (1.8–3.9)


Ethinylestradiol†/drosperidone

2.5 (1.1–5.3)


Ethinylestradiol†/norgestimate

2.3 (0.7–8.2)


Ethinylestradiol†/gestodene

2.2 (1.4–3.3)


Ethinylestradiol†/lynestrenol

2.2 (1.2–4.0)


Oral progestagen only, high dose (5–30 mg)

2.1 (0.6–7.3)


Moderate risk increase (odds ratio 2–5) [7, 108]


Ethinylestradiol†/noresthisterone‡

1.5 (0.5–4.1)


Ethinylestradiol†/levonorgestrel

1.4 (1.1–1.8)


Injectable depot medroxyprogesterone‡

1.4 (0.7–2.8)


Transdermal ethinylestradiol/norelgestromin§

1.5 (0.5–4.1)


No risk increase [12, 109, 110]


Levonorgestrel releasing IUD

0.1 (0.0–0.4)


Progestagen only, low-dose norethisteron 350 μg or levonorgestrel 30 μg

0.2 (0.1–0.4)


Progestagen only, low-dose desogestrel 75 μg¶

0.2 (0.1–0.7)


Uncertain [111]**


Etonogestrel subcutaneous implant

0.5 (0.01–2.9)


Vaginal ring (ethinylestradiol/etonogestrel)

1.5 (0.1–5.4)


HRT


Moderate risk increase (OR 1.5–3.0) [11, 112]


Oral combined estrogen/progestagen pills

2.6 (2.0–3.2)


Oral estrogen only

2.2 (1.6–3.0)


No risk increase [11, 112]


Transdermal (combined estrogen/progestagen and estrogen only) ††

1.2 (0.9–1.7)


Tibolone

0.9 (0.8–1.1)