August 5, 2002
By Janet Wu
Women who use birth control pills come in all shapes and sizes. But that may be a problem when it comes to preventing pregnancies.
Get out of bed, pour some juice and take your birth control pill. It's the daily routine for millions of women like Lisa Kra. As the mother of two active little girls, she says the pill fits her busy lifestyle. "It seemed to work and it didn't provide me any side effects and it was easy," said Kra, who takes birth control pills.
Over the past twenty years, doctors have always taken into consideration lisa's medical history, but never her weight. "More, 'Do you smoke, risk of breast cancer in the family?' That kind of thing, but never my weight," Lisa said.
But a new study from the University of Washington may change that. Researchers found women who weight more than 155 pounds and were taking the pill were twice as likely to get pregnant. And the lower the dose, the higher the risk.
"Overall in the study, three percent of women became pregnant each year who were using oral contraceptives,” said Dr. Robert Barbieri, of Brigham & Women's Hospital. “In the women who weighed more than 155 pounds who were taking the lowest amount of estrogen in their pill, the rate doubled to six percent per year."
It's not quite clear why the extra pounds alter the pill's effectiveness, but researchers suspect heavier women may metabolize the pill more quickly. "It makes sense that if somebody has increased metabolic rate as women who are over 150 pounds do, that they might metabolize the birth control more quickly and have more contraceptive failures," says Ob/Gyn Dr. Sibel Bessim.
If you are over 155 pounds and on the pill, experts say don't panic. "They should look at their pills and if they're on a 20 microgram pill and weigh more than 155 pounds, they probably should contact their physician to talk about the alternatives of taking a 30 to 35 microgram containing pill," said Dr. Robert Barbieri.
Doctors say a little higher estrogen dose shouldn't worry women. Recent studies show current pill doses do not increase the risk of breast cancer. And pills with 30 to 35 micrograms of estrogen are very common. "Those being advertised for acne often have 35 micrograms of estrogen in the pill," said Dr. Bessim.
As for our experts, they said this latest study has them rethinking how they prescribe the pill. Experts say its also important to remember that one of the best ways to ensure the effectiveness of the pill is to take it at the same time every day.