Your Health -- Breast cancer risk and birth control pills

ATLANTA, Georgia (CNN) -- Women with a family history of breast cancer may want to be especially vigilant about getting regular mammograms if they took birth control pills before 1975.

A study published in this week's Journal of the American Medical Association suggests women who fall into both categories may have an increased risk of getting breast cancer.

The study, conducted by Mayo Clinic epidemiologist Thomas Sellers and colleagues, is thought to be the first to evaluate the link between pill use and an inherited risk for breast cancer.

The researchers studied thousands of women from 426 families with a history of breast cancer.

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For women who took birth control pills before 1975, the researchers found a three-fold increase in breast cancer among daughters and sisters of women with the disease.

And there was an 11-fold increase among pill users with an excessive family history -- that is, five or more close relatives with breast or ovarian cancer.

But the researchers stress that only early versions of the pill seemed to have an effect.

"It's only the formulations that were marketed initially in this country that were very high in terms of estrogen and progestin that seem to be influencing the risk," said Sellers.

"When we look at our study population who was exposed to oral contraceptives marketed after 1975, we don't see any suggestion of increased risk," he said.

Hormone dosages in the pill were lowered after 1975.

The Mayo researchers said more research is needed to evaluate any link between use of current birth control pills and breast cancer in families at risk for the disease.

But at-risk women who used the early formulations of the pill should be especially vigilant.

"What this study tells them is if they were exposed to oral contraceptives marketed before 1975, if they haven't been getting their screening mammograms, they have extra incentive to do that," Sellers said.

Birth control pills are one of the leading forms of contraception, second only to sterilization. Some 100 million women use the pill worldwide, according to the journal Population Reports.

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Planned Parenthood Federation of America

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