Combined birth control pill may increase blood clots risk in obese women

Obese women who use oral contraceptives containing oestrogen and progestin have a 24-fold increased risk of venous thromboembolism (VTE) compared with non-obese women not using the drugs, according to a review paper published today in ESC Heart Failure, a journal of the European Society of Cardiology (ESC).

This review article highlights the latest evidence on the independent effects of obesity and contraceptives, and their synergistic effects, on VTE risk and provides clinical recommendations. VTE refers to a blood clot in a vein and includes two life-threatening conditions: deep venous thrombosis and pulmonary embolism.

The World Health Organization estimates that the global prevalence of obesity nearly tripled between 1975 and 2016 – with 15% of adult women being obese. The risk of VTE increases progressively with body mass index (BMI), and in obese women it is more than double that of non-obese women. Obesity has the most substantial impact on VTE women under 40 years of age, who have a five-fold increased risk compared with non-obese women.

Combined oral contraceptives are associated with an elevated likelihood of VTE, with users having a three- to seven-fold elevated likelihood of VTE compared with non-users. In contrast, progestin-only products are not associated with an increased risk of VTE.

The combination of overweight/obesity and use of combined oral contraceptives potentiates the likelihood of blood clots in women of reproductive age. For example, a large population-based study found that overweight and obesity were associated with 1.7-fold and 2.4-fold increased risks of VTE, respectively. However, in combined pill users, the risk of VTE was 12-fold higher in overweight women and 24-fold higher in obese women – when compared with normal weight non-users.

Reference:

Rosano GMC, Rodriguez-Martinez MA, Spoletini I, Regidor PA. Obesity and contraceptive use: impact on cardiovascular risk. ESC Heart Fail. 2022. doi:10.1002/ehf2.14104.