Which Birth Control Pill Is Safest?
Researchers Find Differences in Blood Clot Risk in Different Oral Contraceptives
The new research confirms previous findings and adds new information, says
Ricardo Azziz, MD, chairman of obstetrics and gynecology at Cedars-Sinai
Medical Center in Los Angeles, who reviewed the data for WebMD.
"We know that the combination pills [with estrogen and a progestin] do
increase the risk of thrombosis," he says. It's also known, he says, that women
with an inherited clotting disorder are at higher risk for having a clot if
they take the pill.
But, he adds, overall ''the chances of any woman taking birth control pills
having a deep vein thrombosis is low. Of 10,000 women using the pill, in one
year's time six will have a deep vein thrombosis."
What's also known, he says, is "the longer you use it the less chance of
having a DVT." That might be due to what experts call "selection bias" -- women
who had a problem discontinued using the pill and those who remain on it are
simply less prone to blood clotting problems.
What is also important to understand, Azziz says, is that even if the risk
of blood clots from one type of pill is twice or more that of another, "We are
talking about twice the risk for something that is quite rare to begin
Women shouldn't go off the pill based solely on the new findings, he says.
What is crucial, he says, is for a woman's doctor to prescribe the birth
control pill that's best for her, the one that will be linked with the least
side effects. "Some patients will do better on some pills than others," he
Starting with the lower-dose estrogen pills and the ones with progestins
found linked with the least risk is wise, he says. To start with, he suggests
pills with levonorgesterol or norethisterone and a low dose of estrogen.
The risks associated with not taking the pill, including unwanted pregnancy
and pregnancy complications, may be higher than the risk associated with its
use, Azziz says.
Oliver Renner, a spokesman for Bayer Schering Pharma in Berlin, which makes
oral contraceptives, says the company is in the process of evaluating the data
and needs time to respond.