In the more liberal western regions of the country, the association between abortion and breast cancer was statistically insignificant. Another article, published in the Journal of the National Cancer Institute in 1994, illustrates the difficulty of drawing conclusions. In this study, Daling and others evaluated the risk of breast cancer among young women with a history of abortion. Risk did not vary consistently with number of abortions, the woman's age at abortion or length of pregnancy, nor did the study show an increase in risk associated with spontaneous abortions. Because the evidence is weak and inconsistent, researchers cannot be sure that there is a direct or causal relationship between abortion and breast cancer.
Obesity is a risk factor for breast cancer in postmenopausal women.
The increased risk of developing breast cancer associated with each factor varies, from 1.5 to 4 times the average risk. Reproductive factors in the aetiology of breast cancer. Daling JR, Malone KE, Voigt LF, et al. Reproductive factors and breast cancer. Lindefors-Harris BM, Eklund G, Adami HO, et al.