Beral V (July 20, 2002) The Lancet, 360:187-95.
Comments: A meta-analysis of 47 epidemiological studies conducted in 30 countries in which Beral reported that, "The relative risk of breast cancer decreased by 4.3% (95% CI 2.9-5.8; p<0.00001) for every 12 months of breastfeeding in addition to a decrease of 7.0% (5.0-9.0; p<0.0001) for each birth. The size of the decline in the relative risk of breast cancer associated with breastfeeding did not differ significantly for women in developed and developing countries, and did not vary significantly by age, menopausal status, ethnic origin, the number of births a woman had, her age when her first child was born, or any of nine other personal characteristics examined. It is estimated that the cumulative incidence of breast cancer in developed countries would be reduced by more than half, from 6.3 to 2.7 per 100 women by age 70, if women had the average number of births and lifetime duration of breastfeeding that had been prevalent in developing countries until recently. Breastfeeding could account for almost two-thirds of this estimated reduction in breast cancer incidence."
Interpretation: "The longer women breast feed the more they are protected against breast cancer. The lack of or short lifetime duration of breastfeeding typical of women in developed countries makes a major contribution to the high incidence of breast cancer in these countries."
"Beral V, Bull D, Doll R, Peto R, Reeves G. Collaborative Group of Hormonal Factors in Breast Cancer. Breast cancer and abortion: collaborative reanalysis of data from 53 epidemiological studies, including 83,000 women with breast cancer from 16 countries. Lancet 2004;363:1007-16.
Patrick Carroll, et al. (2001) "Abortion and Other Pregnancy Related Risk Factors in Female Breast Cancer," Pension and Population Research Institute, London.
"We believe (the incidence of breast cancer) can be better explained if abortion is recognized as a relevant risk factor alongside other pregnancy