A new study has shown that women who use new type of contraceptive pills are twice as likely to develop life threatening blood clots as those who take older versions. Oral hormonal contraceptives have been known to increase the risk of a blood clot in deep leg veins, known as venous thromboembolism (VTE). These can prove fatal if they travel to the lungs. But, researchers at the University of Copenhagen, Denmark, found the “third-generation” pills are doubly harmful than the older versions.
The team of researchers looked at contraception records and cases of blood clots between 2001 and 2009 for millions of women aged between 15 and 49. They found 4,246 women who suffered their first VTE during that time. They noted a risk of clots raised threefold among those who took old-style pills containing levonorgestrel, and six-fold among those on the newer type. The study was published in BMJ.com.
The US Food and Drug Administration (FDA) today released the final report of an FDA-funded study looking into the risk for venous thromboembolism (VTE) in women taking oral contraceptives containing drospirenone.
Earlier reports from FDA’s preliminary findings on September 26 from the study indicate that women who use drospirenone-containing birth control pills have an approximately 1.5-fold increase in the risk of developing blood clots relative to women using other types of hormonal contraceptives. However, the agency said its review of the study was ongoing.
According to the report posted now, the final results add to the “increasing body of evidence” linking drospirenone/ethinyl estradiol (DRSP) tablets to increased risk for VTE relative to standard low-dose combined hormonal oral contraceptives.
In the study, “DRSP was associated with higher risk of [arterial thrombotic event] in new users overall with this finding restricted to women in the 35-55 years age group only,” the agency notes. According to the FDA, the findings also “add to the small body of literature” that shows that the norelgestromin/ethinyl estradiol (NGMN) transdermal patch is associated with higher risk for VTE compared with standard combined hormonal oral contraceptives.
The findings also point to an increased risk for VTE with the etonogestrel/ethinyl estradiol (ETON) vaginal ring relative to standard combined hormonal contraceptive pills. This finding, the agency says, is “new and raises concern but needs to be replicated in other studies.”
The FDA says the findings from the study will be presented and discussed at the joint meeting of the Reproductive Health Drugs Advisory Committee and the Drug Safety and Risk Management Advisory Committee on December 8.
Drospirenone is in the contraceptive pills Beyaz, Gianvi, Loryna, Ocella, Safyral, Syeda, Yasmin, Yaz, and Zarah. Desogestrel is in Ortho-Cept, Cyclessa, Deogen, Emoquette, Kariva, Mircette, and Velivet. Gestodene is not approved for use in the U.S.
“This is one of several studies that have shown that certain birth control pills have higher risks of blood clots over other birth control pills,” says Jennifer Wu, an obstetrician/gynecologist at Lenox Hill Hospital in New York City, who was not involved in the research. “I think women really need to talk with their doctors before they start a birth control pill, and doctors should try to choose ones that have lower risks…I wouldn't start with these riskier oral contraceptives as first-line, first-start pills,” she said.
Because so many women take birth control pills, even small risks can have significant public health consequences. “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,” says researcher Ojvind Lidegaard, professor of obstetrics and gynecology, Rigshospitalet at the University of Copenhagen, in Denmark. “And you could actually halve that number just by changing the pill from a fourth- to a second-generation pill.”
But experts say switching to an older pill may not be the best option for every woman. “It is important to have a range of different oral contraceptives available because some women tolerate one preparation better than another,” Philip C. Hannaford, who is the Grampian Health Board chair of primary care at the University of Aberdeen, in Scotland, said. Some women prefer one kind of pill over another, Hannaford says, because they experience less nausea, 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,” says Hannaford, who was not involved in the research but wrote an editorial on the study.
Smoking, being overweight, family history, and age also increase the risk of blood clots. Those risks should be discussed with a doctor before starting or switching any kind of hormonal contraception. Women who are on birth control pills should also be aware of the symptoms of blood clots. Symptoms of a blood clot in the leg can include pain in the calves from walking and one leg swelling larger than the other.
“One of the symptoms patients really need to look out for is shortness of breath because one of the huge risks with DVT is that the clot can travel to the lungs, and that can kill people,” Wu said. “Even though the risk overall is low, I think that the possible consequences are pretty dire. Patients on these riskier birth control pills should know the symptoms to look for.”
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