Familial risk of breast cancer and abortion.

We found that the risk of breast cancer associated with a family history of breast cancer increased with the number of abortions (induced as well as spontaneous) in a study of 495 breast cancer cases and 785 controls aged 20 to 56 years. For the women who had undergone at least two abortions, the risk associated with a family history did not seem to depend on the type of abortion. This finding suggests that the effect of a family history on the risk of breast cancer is modified by event(s) resulting from abortions. Further epidemiological studies should be conducted to verify the existence of this interaction.