Recent findings show newer formulations of oral contraceptives could double blood clot risk for women taking them compared with older versions of the drugs, says a study published in the journal BMJ and reported by the Huffington post.

Research confirms that women who take any kind of birth control are at greater risk of not only heart attack and stroke, but also venous thromboembolism, or VTE. VTE causes blood clots to develop in the legs (called deep vein thrombosis) or travel to the lungs (called a pulmonary embolism) and can stop a person’s breathing.

For the study, researchers looked at medical records for more than 10,000 women with VTE from two large patient databases in the United Kingdom. Scientists found that the women in this group who took combined birth control pills with newer progesterone types (including desogestrel, gestodene, drospirenone and cyproterone) were about twice as likely to develop blood clots than those who took older contraceptive combos (containing drugs like norgestimate, or levonorgestrel and norethisterone).

The findings also showed that patients on any form of hormonal birth control pills were three times more likely overall to develop VTE than women who weren’t taking any oral contraceptives. Still, researchers said it’s important to note that VTE rarely occurs and women taking birth control pills shouldn’t stop or change their treatment without consulting their doctors and risk an unplanned pregnancy.

Concluded Yana Vinogradova, PhD, a research fellow at the University of Nottingham and one of the study’s authors, “Combined oral contraceptives remain effective and relatively safe drugs—significantly safer in terms of risk of VTE than either pregnancy terminations or pregnancy itself.”

For more information about the risks and benefits of birth control, click here.