Obese women who use oral contraceptives may be at greater risk for cerebral venous thrombosis (CVT), compared with women of normal weight who do not use oral contraceptives (OCs). Findings of this study were published online by JAMA Neurology.

Jonathan M. Coutinho, MD, PhD, of the Academic Medical Centre, Amsterdam, the Netherlands, and coauthors studied patients with CVT from two hospitals. The study included 186 case patients with CVT and 6,134 healthy controls for comparison. Compared with controls, the case patients were younger, more often female, more frequently had a history of cancer and more often used OCs.  Obesity (BMI ≥30) was associated with increased risk of CVT  (adjusted odds ratio [OR], 2.63; 95% CI, 1.53-4.54) and this association appeared to be due to a strongly increased risk in women who used OCs. Compared with women of normal weight who did not use OCs, there was a nearly 30-fold increased risk of CVT among obese women taking OCs. While there was no association between obesity and CVT among men or women not on OCs, there was an increased risk of CVT in overweight women who used OCs.

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CVT is a rare thrombotic condition and risk factors partly overlap with those for venous thromboembolism (VTE); various studies have identified obesity as a risk factor for VTE. This is the first case-control study to examine the link between obesity and CVT.

“The increased risk of VTE and CVT associated with oral contraceptives in the presence of obesity might make physicians reluctant to prescribe oral contraceptives to obese women. However, although the relative risks are increased substantially, the absolute risks of CVT are small. Moreover, withholding oral contraceptives may lead to an increase in unintended pregnancies and thus the number of pregnancy-related thrombosis cases. Nevertheless, obese women should be informed about the increased risk of thrombosis if they use oral contraceptives, especially if other risk factors are present. Alternative methods of contraception that are not associated with thrombosis, such as intrauterine device, might be offered to these women,” the authors conclude.

For more information visit JAMA Neurology.