The newer contraceptive birth control pills appear to double the risk of blood clots says new research.
One of the largest studies to look at the link better "the pill" and blood clots, showed the older formulas to have a lower risk, but the newer versions to perform better in regards to venous thromboembolism (VTE). The researchers stressed that women should consult their doctor before changing brands or formulas.
Blood clots can be particularly dangerous because once formed in a peripheral vein, usually in the leg, the clot can break free and travel to more sensitive parts of the body, such as brain or vital organs.
Medical records of close to 1.3 million women were included in the study, with 30% of them never having used hormonal contraception, while nearly 70% had used some form of hormonal birth control.
Of the total, 4,307 cases of blood clots required treatment with (64%) as deep vein thrombosis (DVT), where a blood clot chokes circulation in a limb, causing a leg or arm to become swollen, stiff, or painful. 25% were blood clots in the lungs. Around 2% had blood clots that caused strokes.
The older-generation pill that contains an estrogen and the progestin hormone levonorgestrel roughly doubled the risk compared to women not on any hormonal birth control.
The newer kinds of pills, which contain the progestin hormones drospirenone, desogestrel, or gestodene along with estrogen, doubled the risk again, making it six to seven times as high as women who weren't using hormonal forms of birth control. On average, roughly 10 out of 10,000 women taking newer kinds of birth control pills had venous thromboembolism within a year.
The study which is probably going to trouble doctors, patients and drug companies alike, was published in BMJ, just as the FDA is reviewing the safety of newer birth control pills. The FDA birth control investigation was announced in May 2011 and is scheduled to be finished shortly.
In September, the agency said it had not yet reached a conclusion but :
"remains concerned about the potential increased risk of blood clots with the use of drospirenone-containing birth control pills."
The problem is that the wide use of the birth control pill can create a real public health problem even if its only small number statistically. Researcher Ojvind Lidegaard, MD, professor of obstetrics and gynecology, Rigshospitalet at the University of Copenhagen, in Denmark said : "
"You have to consider that 200 million women, every day, worldwide take such a pill. So even if it's only one in 500 per year who get the thrombosis if they are on a fourth-generation pill and are 30 years old, then you actually get a relatively high number of complications .... and you could actually halve that number just by changing the pill from a fourth- to a second-generation pill."
But experts say changing back to an older version of the pill may not be the smartest choice for all women. Philip C. Hannaford, MD, who is the Grampian Health Board chair of primary care at the University of Aberdeen, in Scotland, says in an email to WebMD.
"It is important to have a range of different oral contraceptives available because some women tolerate one preparation better than another."
Obviously some women prefer one kind of pill over another for practical daily reasons such as less nausea, fluid retention, acne, or weight gain.
"This means that clinicians and women often chose to use combined oral contraceptives which do not contain levonorgestrel, and this seems a pragmatic and sensible thing to do given that the background risk of DVT is very low."
It would also be important for women and their health care professionals to take into account other factors, such as medical history, family history and other risk factors such as smoking, alcohol consumption, weight and general health.
Written by Rupert Shepherd