New contraceptives raise risk of blood clots by 50 to 80 percent: British study
May 29, 2015 (LifeSiteNews.com) – Women who use modern contraceptives have at least a 50 percent greater chance of having potentially deadly blood clots, according to a new study published in the British Journal of Medicine.
The study -- which examines women aged 15-49 over the last 13 years -- used two different United Kingdom databases to examine how frequently women developed blood clots while using new combined contraceptives, as compared to older contraceptives.
"Risks for women using newer pills were around 1.5-1.8 times higher than for women using older pills," according to a press release announcing the study's results. "In absolute terms, the number of extra [blood clot] cases per year per 10,000 treated women was lowest for levonorgestrel and norgestimate (six extra cases), and highest for desogestrel and cyproterone (14 extra cases)."
A BJM editorial about the study noted that the results showed "newer contraceptives increased risks by around 3.6- to 4.3-fold compared with non-use, and by around twofold compared with oral contraceptives containing levonorgestrel, norethisterone, or norgestimate."
"Combined, the results provide compelling evidence that these newer oral contraceptives are associated with a higher risk of venous thromboembolism than older options, despite attempts to develop safer hormonal contraceptives for women," concluded the BJM editorial.
The report's lead author, University of Nottingham Research Fellow Yana Vinogradova, told LifeSiteNews in an email that "the risk [of blood clots] is 2.4-2.5 times higher in women taking old contraceptives compared with no use."
The author told LifeSiteNews that "in each database, there were about 3 million women 15-49 years old, and more than 5,000 of them had [a blood clot]." The study said that 28 percent of women in the United Kingdom use contraceptives.
Despite the higher risk, the release also says that "the authors stress that oral contraceptives are remarkably safe, and...the reported three-times increased risk of VTE in women using oral contraceptives in their study is still lower than the up to 10-fold increased risk of VTE in pregnant women."
The study is just the latest to find significant potential harm from using modern contraceptives. Last year, a study found that high-dose estrogen pills "increased breast cancer risk 2.7-fold," while "those containing moderate-dose estrogen increased the risk 1.6-fold."
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Likewise, a 2014 Centers for Disease Control (CDC) study found a possible link between hormonal contraceptives and gestational diabetes, and a 2013 CDC study found a possible connection between use of the birth control pill and glaucoma.
Despite the higher risks of blood clots among women who use contraceptives, especially newer forms, Vinogradova defended the study's finding that "this is an observational study so no definitive conclusions can be drawn about cause and effect."
"Definite conclusions can be drawn only from a randomized controlled trial where patients with known and unknown risk factors are randomly allocated into the arms," she wrote. "Conducting a randomized controlled trial in these circumstances is not feasible, therefore only observational studies can be performed. In observational studies, exposed and non-exposed participants may have different risk factors for outcome."
"Although we considered all available from the databases risk factors, there may be other unknown or not-available ones. So the estimates of risks associated with different types of contraceptive pills provided by our study are the most accurate to date."