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Birth Control Health Center

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Study: Newer Birth Control Pills May Double Blood Clot Risk

Overall Risk Is Still Low, but May Be Highest During the First Few Months of Use

Advice to Women continued...

“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,” Wu says. “I wouldn’t start with these riskier oral contraceptives as first-line, first-start pills.”

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, MD, 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, MD, who is the Grampian Health Board chair of primary care at the University of Aberdeen, in Scotland, says in an email to WebMD.

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 says. “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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