A report on the risk factors for breast cancer published by the Journal of Dhaka Medical College in Bangladesh has determined that women who have induced abortions increase their chances of getting cancer by as much as 20 times.
"Almost all the women are married (97% currently married; the rest widowed) and with child by the time they are 20, and all of the kids are breastfed. Ninety percent had their first child at age 21 or younger (99% of controls did)," explained Professor Joel Brind of Baruch College, City University of New York, noting that the high risk elevation is a measure of relative risk and that in general, Bengali women have traditional childbearing patterns that reduce breast cancer risk.
"They typically neither take contraceptive steroids nor have any abortions. Nulliparity (childlessness) or abortion before first full term pregnancy (both of which mean no breastfeeding) in a population in which breast cancer is almost unheard of, makes the relative risk very high," Brind continued, who is a professor of biology and endocrinology.
The raw data of the study, reported by the Coalition on Abortion/Breast Cancer, showed a 95 percent confidence interval of 12.85-32.51, which makes abortion the strongest risk factor observed in the women who were studied.
"In plain English, women in this population who had any induced abortions were more than 20 times as likely to get breast cancer, compared to women with no abortions," Brind added.
Other factors that might influence the risk of breast cancer include use of oral contraceptives (1.47-fold increased risk); early first birth at or before age 21 (0.35-fold reduced risk); having two or more children (0.29-fold reduced risk); and increased number of months spent breastfeeding (0.30-fold reduced risk), according to the Journal report.
Various other studies have been done on the link between abortion and the risk of breast cancer, coming up with different results, and some showing no link at all.
The American Congress of Obstetricians and Gynecologists said in a June 2009 report that the topic has been the subject of a great deal of epidemiologic study, but noted that "more rigorous" recent studies have failed to demonstrate a casual relationship between induced abortion and an increase in breast cancer risk.
"In 2003, the National Cancer Institute convened the Early Reproductive Events and Breast Cancer Workshop to evaluate the current strength of evidence of epidemiologic, clinical, and animal studies addressing the association between reproductive events and the risk of breast cancer," ACOG wrote.
"The workshop participants concluded that induced abortion is not associated with an increase in breast cancer risk. Studies published since 2003 continue to support this conclusion."
The Breast Cancer Prevention Institute, on the other hand, compiled a list of 68 different worldwide studies since 1957 that analyzed the supposed link between induced abortion and the development of breast cancer. Of those studies, 53 showed some kind of association, while 15 studies did not show such a link.