Based on the results of a recent study researchers say evidence does not suggest any increase in the risk of developing breast cancer for women who have had a spontaneous or induced abortion.Researchers found the average relative risk of breast cancer was .98 for women whose pregnancies ended in miscarriage and .93 for women who had a pregnancy that ended as an induced abortion. A relative risk of 1.0 or less indicates no adverse effect on the subsequent risk of breast cancer. The number of abortions was also not associated with any change in breast cancer risk.
In a recent study researchers re-analyzed data from 53 epidemiological studies in 16 countries. Information was available from 44,000 women who had taken part in studies where any history of abortion had been recorded long before breast cancer was diagnosed. Data on 39,000 women with breast cancer, where women were asked after breast cancer diagnoses about any previous abortions, gave misleading results, on average. Investigators say this may be because women with breast cancer are more likely than other women to disclose any prior induced abortions.
However previous studies show pregnancies that result in a birth reduce a woman's long-term risk of developing breast cancer.