Study Examines Which Birth Control Pills Are Safest for Women With High BMI

Women with high body mass index (BMI) who use the combined estrogen/progestin tablet are 24 times more likely to experience life-threatening blood clots, according to new research from Italy.

The risk was found to be 12 times higher in those women who are overweight. The findings come from women of childbearing age.

The combined birth control pill contains a synthetic version of estrogen, a hormone that can cause venous thromboembolism (VTE). The condition reduces blood flow to organs, potentially triggering heart attacks or strokes.

Doctor holding birth control pills
Stock image of a doctor holding birth control pills. Researchers suggest that a woman's weight should be considered with their prescription for birth control pills. Ground Picture/Shutterstock via Zenger

Lead author Professor Giuseppe Rosano, of the IRCCS San Raffaele Pisana in Rome, 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 obesity and combined oral contraceptives have a synergistic effect on VTE risk and this should be considered in prescribing decisions."

He advised them to use the "mini-pill" - which only has chemicals that mimic the hormone progestin - or other methods. Both prevent pregnancy.

Women who have had breast cancer, have previously suffered blood clots, or have a family history of either are already precluded from the combined pill. "Progestin-only products, including pills, intrauterine devices or implants are a safer alternative to the combined pill in women carrying excess weight," Rosano said.

The study appears in the European Heart Journal (EHJ). The article is based on a review of the latest evidence.

The researchers found they are nearly twice and two-and-a-half times more likely to develop blood clots, respectively. However, in combined pill users, the risk rose twelve and 24 times respectively when compared with non-users with a BMI in the normal range.

"This article highlights the latest evidence on the independent effects of obesity and contraceptives, and their synergistic effects, on VTE risk and provides clinical recommendations," Rosano said.

She said that "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 (WHO) estimates global prevalence of obesity nearly tripled between 1975 and 2016, with 1 in 7 women being obese. The risk of VTE increases progressively with BMI - more than doubling in obese women. The biggest impact occurs in those under 40, soaring fivefold.

Rosano said: "The particularly high risk in obese women under 40 is important since it is at this age that many seek contraception." Overall, the combined pill is linked to increasing the likelihood of VTE three to seven times. There is no link between the mini-pill and blood clots.

"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," Rosano said.

Drug company executives have been accused of holding back the British launch of a pioneering pill that could transform birth control.

The medication, Slynd, contains progestin only, causes fewer side effects and is more effective than the mini-pill. It can be used at any time during a 24-hour period. Others have to be taken during a short window every day.

The revolutionary tablet has been widely available in America and Australia since 2019 and received its U.K. license in March last year from the Medicines and Healthcare Products Regulatory Agency. But manufacturer Exeltis is not expecting it to be available in the U.K. until at least next year.

Financial watchdog NICE (National Institute for Health and Care Excellence) will have to approve prescriptions via the U.K.'s National Health Service.

Produced in association with SWNS Talker.

This story was provided to Newsweek by Zenger News.