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Birth Control Pills Increase Blood Clot Risk in Women with PCOS

young woman looking at birth control tablets

A new study in the Canadian Medical Association Journal found that women with polycystic ovarian syndrome (PCOS) have twice the risk of developing a blood clot when taking oral birth control.

One of the study researchers, Dr. Christopher McCartney, told Reuters: “For some women, [the risks] might be high enough to say we really shouldn’t use the pill, such as for women over 35 who smoke.”

PCOS affects 5-10 percent of women and occurs when there is an imbalance of the sex hormones: estrogen, progesterone and androgen. Some of the symptoms of this condition are cysts on the ovaries, irregular menstrual periods, extra hair growth as well as higher risk of obesity, hypertension and diabetes. According to Reuters, women with PCOS also have more risk factors for heart disease.

The study began in 2001 and involved 43,506 women with PCOS who were between the ages of 18 and 46. Researchers compared the health information from the women with PCOS with information gathered from 43,506 women without PCOS. They found the risk of blood clots for women on oral contraceptives with PCOS was double that of women without PCOS.

Other findings also indicated that women with PCOS were more likely to be obese – 33 percent more likely, in fact. McCartney told Reuters: “I really think [obesity] could be something that’s contributing to the risk.”

Doctors Warn About Blood Clot Risk with Drospirenone

The fact that oral contraceptives can cause blood clots in some women is not new news, however. The hormones in the newest generation of birth control pills containing drospirenone, such as Yaz, Yasmin and Ocella, have been linked to a higher risk of blood clots than older pills.

A 2011 study, also published in the Canadian Medical Association Journal, showed that drospirenone raises women’s blood clot risk by a stunning 40 percent. Another study that appeared in Contraception in October 2012 found that this hormone also increased the risk of hospitalization from venous thromboembolic events (VTEs), more commonly known as blood clots, by 77 percent.

The lead author of the Contraception study, Dr. Stephen Sidney, is director of Research Clinics at Kaiser Permanente Northern California. Science Daily quoted Dr. Sidney: “The growing number of studies showing an increased risk of venous thromboembolic events with drospirenone suggests that drospirenone-containing combined hormonal contraceptives should be used cautiously for women seeking hormonal contraception.”

Doctors say that these studies are not meant to encourage women to not take the contraceptives, but that the risks and benefits should be carefully weighed in high-risk women.

However, the dangers of these newer birth control pills, particularly Bayer’s Yaz and Yasmin and their generic counterpart, Ocella, have prompted some women and their families to file suit against the drugmaker. Plaintiffs and their families accuse Bayer of concealing the risks of blood clots – some fatal – and misrepresenting the risks and benefits of these drugs.

Last modified: November 16, 2017


Michelle Y. Llamas is a senior content writer. She is also the host of Drugwatch Podcast where she interviews medical experts as well as patients affected by drugs and medical devices. She has written medical and legal content for several years — including an article in The Journal of Palliative Medicine and an academic book review for Nova Science Publishers. With Drugwatch, she has developed relationships with legal and medical professionals as well as with several patients and support groups. Prior to writing for Drugwatch, she spent several years as a legal assistant for a personal injury law firm in Orlando. She obtained her English – Technical Communication degree from the University of Central Florida. She is a committee member with the American Medical Writers Association.

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  1. Huffington Post. (2012, December 3). Blood clot risk higher for women with polycystic ovarian syndrome who take birth control pill: Study. Retrieved from
  2. Grens, K. (2012, December 3). Hormone disorder and the pill tied to blood clots. Reuters. Retrieved from
  3. Science Daily. (2012, October 18). Elevated risk of blood clots in women taking birth control containing drospirenone.