Abortions do not increase risk for breast cancer

A new study by researchers at Harvard supports earlier findings by a panel of experts that abortions and miscarriages do not increase a woman's risk of getting breast cancer.

Lead author Karin Michels of Brigham and Women's Hospital and Harvard Medical School in Boston conducted a prospective study, starting with women before they ever had cancer, and following them for years.

The study began with 105,000 U.S. nurses aged 29 to 46 years in 1993 who were all cancer-free; they completed a detailed, anonymous questionnaire that included questions about abortions and miscarriages.

Other studies have started with women who already had breast cancer and asked them whether they had ever had an abortion and the researchers believe such women are much more likely to report this.

Abortion is one area that women are likely to underreport because it is such a sensitive issue, says Michels.

The study found that 15 percent of the nurses reported they had had an abortion and 21 percent reported a miscarriage.

Over the 10 years of the study, 1,458 of the women developed breast cancer, and Michels' team found that those who had an abortion or miscarriage were no more likely to have breast cancer than any other woman in the study.

Despite a group of scientists acting for the National Cancer Institute concluding in 2003 that abortion did not raise the risk of breast cancer, states opposed to abortion still demand doctors warn women seeking abortions of a link to breast cancer.

This latest analysis is unlikely to convince the states of Texas, Minnesota and Mississippi to change their approach to women seeking abortions.

Breast cancer is far more common after menopause, but Michels' team noted that the studies that had seemed to show abortion caused breast cancer also mostly looked at younger women who had not reached menopause.

Researchers had good reasons to suspect that abortion and miscarriage might possibly be linked to breast cancer as they believed the roller-coaster of hormonal changes in pregnancy, when interrupted, might encourage breast cells to turn cancerous.

But the evidence shows that childbearing before the age of 35 reduces a woman's breast cancer risk and breast-feeding also helps, as scientists believe breast cells that have gone through a full-term pregnancy gain protection against cancer.

The study is published in the Archives of Internal Medicine.