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The Pill May Raise Breast Cancer Risk

Analysis Suggests Small Increase in Risk When Oral Contraceptives Used Before First Pregnancy
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WebMD Health News
Reviewed by Louise Chang, MD

Oct. 31, 2006 -- Women who take oral contraceptives have a slightly increased risk of developing breast cancer early in life, with the risk being greatest for women who use oral birth control before they have their first child, a new analysis suggests.

Researchers combined the findings from 34 previous studies designed to examine the impact of oral contraceptive use on breast cancercancer diagnosed before menopausemenopause.

Twenty-one of 23 studies that followed women who took oral birth control before having their first child showed an increased risk of early breast cancer.

Measuring Risk

Based on these studies, the researchers concluded that taking oral contraceptives before a first full-term pregnancypregnancy increases premenopausal breast cancer risk by 44%, compared with women who have never used oral contraceptives.

The increase in risk was 52% among women who took the pill for four years or more before having their first child.

"I think women should know about this risk, and they are not being told," researcher Chris Kahlenborn, MD, of Altoona Hospital in Altoona, Pa., tells WebMD.

"Anyone who is prescribing oral contraceptives has a duty to tell women that 21 out of 23 studies showed an increased risk."

Breast cancer is most often diagnosed in women over the age of 50, but cancers that occur in younger women tend to be more aggressive. It is the leading cancer killer among women between the ages of 20 and 59 in the U.S.

Kahlenborn says he conducted the analysis because he believes far too few women know the risks associated with oral contraceptive use.

"As I studied the medical literature, I noticed that a trend appeared," he says. "Namely, oral contraceptive use prior to first full-term pregnancy seemed to consistently increase the risk of premenopausal breast cancer. Although the trend was apparent, premenopausal women have continued to hear that oral contraceptives are safe."

The 34 studies chosen for the analysis included women who were premenopausal or younger than 50 whose breast cancers had been diagnosed during or after 1980.

Studies examining breast cancers diagnosed before this were excluded in an attempt to approximate the risk with oral contraceptives as they are currently prescribed.

When all the studies were combined, use of oral birth control was associated with a 19% overall increased risk of breast cancer diagnosed before menopause. But the increase in risk more than doubled among women who took oral contraceptives before a first pregnancy.

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