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