Combined birth control pill greatly increases the risk of blood clots in obese women.
According to a paper recently published in ESC Heart Failure, a journal of the European Society of Cardiology, obese women who use oral contraceptives containing estrogen and progestin have a 24-fold increased risk of venous thromboembolism (VTE) compared to non-obese women who do not use the drugs.
Study author Professor Giuseppe Rosano of the IRCCS San Raffaele Pisana, Rome, Italy said: “It is well established that both obesity and estrogen-containing contraceptives are risk factors for VTE. Despite this, obese women continue to receive these drugs. The scientific evidence indicates that obesity and combined oral contraceptives have a synergistic effect on VTE risk and this should be considered in prescribing decisions. Progestin-only products, including pills, intrauterine devices, or implants are a safer alternative to the combined pill in women carrying excess weight.”
This review article highlights the most recent research on the individual effects of obesity and contraceptives, as well as the combined impact of these factors, on the risk of VTE and offers clinical recommendations. VTE refers to a blood clot in a vein and encompasses two potentially fatal conditions: deep venous thrombosis and pulmonary embolism.
According to the World Health Organization, the percentage of adult women who are obese almost quadrupled between 1975 and 2016. The risk of VTE grows progressively with body mass index (BMI), and it is more than double in obese women compared to non-obese women. Obesity has the greatest effect on VTE women under 40, who have a five-fold greater risk compared to non-obese women.
Professor Rosano noted: “The particularly high risk in obese women under 40 is important since it is at this age that many seek contraception.”
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 the 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 being overweight and obese was 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.
Professor Rosano said: “Obese women taking contraceptives are vulnerable to VTE and should take steps to limit their other predisposing factors for cardiovascular disease, for example by quitting smoking and increasing their physical activity levels.”
Reference: “Obesity and contraceptive use: impact on cardiovascular risk” by Giuseppe M.C. Rosano, Maria Angeles Rodriguez-Martinez, Ilaria Spoletini and Pedro Antonio Regidor, 14 September 2022, ESC Heart Failure.