Birth control pills linked to a higher risk of blood clots in obese women

Birth control pills linked to a higher risk of blood clots in obese women
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A new study finds that obese women who use combined birth control pills have an increased risk of blood clots compared to non-obese women.

Researchers have discovered that obese women taking combined birth control pills that contains oestrogen and progesterone have a 24-fold increased risk of venous thromboembolism (VTE) compared with non-obese women not using this medication. This finding was published in ESC Heart Failure, a journal of the European Society of Cardiology (ESC).

Study author Professor Giuseppe Rosano of the IRCCS San Raffaele Pisana, Rome, Italy said: “It is well established that both obesity and oestrogen-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, which 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.”

What is the combined birth control pill?

The combined birth control pill contains artificial versions of female hormones oestrogen and progesterone; both are produced naturally in the ovaries. 

Birth control pills aim to stop the sperm from reaching the egg by keeping them apart or by stopping the release of the egg.

The pill is believed to be 99% effective at preventing pregnancy.

Increased risk of blood clots in obese women

The new review provides vital evidence of the independent effects of obesity and birth control pills and their synergistic effects, on VTE risk and provides clinical recommendations. 

Obesity rates continue to rise, with data illuminating that 15% of adult women are obese. Furthermore, the risk of VTE increases with body mass index (BMI), therefore, this puts obese women at higher risk regardless of birth control consumption. Concerning data has also confirmed that obesity puts women under 40 years old at a five-fold increased risk of VTE 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 birth control pills are associated with an elevated likelihood of VTE, with users having a three-to-seven-fold elevated likelihood of VTE compared with non-users. Contrastingly, progesterone-only products are not associated with an increased risk of VTE.

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.

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.”

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