Pregnancy, Abortion and Breast Cancer

By Lyn Smith

There is a public perception that when abortion is legal, abortion is safe. The media seldom focuses on the long term psychological and physical effects on a woman's health should her pregnancy be interrupted by induced abortion.

image-058Nevertheless, in a 1994 article in the Ottawa Citizen, registered nurse and journalist, Nancy Lloyd, quoted Dr. Norman Barwin, infertility specialist and past president of Planned Parenthood Canada, as saying, "Abortion is an invasive medical procedure. Every patient should be told of the risks and benefits of the procedure. It is often too late afterwards to have guilty feelings and regrets." He observed that there can be medical complications from abortion. The complications can be caused by the abortion technique, secondary infection and bleeding which can result in subsequent infertility. Dr. Myron K. Denney, in a discussion of the various risks of abortion says in his book, A Matter of Choice:An Essential Guide to Every Aspect of Abortion, "Even without injury, abortion taxes the normal bodily protective mechanism."

Evidence has begun to surface in the English scientific literature that research which dates as far back as 1957 indicated that there was another risk to women's health: women who have undergone an induced abortion before a full term pregnancy have an increased risk for developing breast cancer (Japan, Segi et al - GANN). In 1981 a landmark study was conducted by Malcolm Pike, M.D. and colleagues at the University of Southern California. Abortion had been legalized in the U.S. in 1973 and Pike's data collection period covered 1972-1978. The study was restricted to women less than 33 years old who aborted before a first full pregnancy. Pike found these women to be 2.4 times more likely to develop breast cancer than those with no history of induced abortion.

Researchers acknowledge that one in nine (1 in 9) Canadian and American women will be diagnosed with breast cancer in her lifetime. Despite improved methods for early diagnosis and a rigid emphasis on self-examination and mammography, the number of new cases of breast cancer continues to rise each year. There are some universally accepted risk factors for the development of breast cancer: never having a child, delayed child bearing, early menstruation and late menopause, family history of breast cancer, and aging. Even so, "The very grim fact remains that in 60 to 70% of women diagnosed with breast cancer not one of the risk factors is present." (1992 Canada Report of the Standing Committee on Health and Welfare, Social Affairs, Seniors and the Status of Women: Breast Cancer: Unanswered Questions).

Is there a new factor in the medical histories of Canadian women? Abortion was decriminalized in 1969. We know that the number of new breast cancer cases has risen every year and this rise is paralleled by the increasing numbers for induced abortions reported each year by Statistics Canada. Abortions increased from 69,499 in 1984 to 106,255 in 1994. The number of new breast cancer cases reported for the first time nationally in 1984 was 10,321 and rose to 17,000 in 1994. It was estimated that in 1996 there would be 18,600 new cases of breast cancer and that 14 Canadian women would lose their life to breast cancer each day. Most abortions are done in the first trimester when the breast cells are the most unstable and over 50% are done on women who have no prior pregnancy so that they are without the protection of a full term pregnancy. In the last 20 years, the share of abortions has increased for women who had been pregnant less than 13 weeks, for women in their 30's and for those women who had at least one prior induced abortion. Statistics Canada now estimates (1994) that one woman in three will have an abortion in her lifetime.

Scientists agree that the earlier in a woman's life that her breast cells reach maturity due to a full term pregnancy, the more protected she is against the possibility of developing breast cancer. Breast cancer is believed to originate in undifferentiated or primitive cells. Prior to conception a woman's breasts consist mostly of connective tissue surrounding a branching network of ducts with relatively few milk producing cells. At conception there is a surge of oestradiol or estrogen production and the milk buds begin to develop a duct-like form preparatory to lactation at birth. During the first trimester the breast cells are in a 'transitional' or undifferentiated stage and are vulnerable to cancer until the cells begin to differentiate or 'specialize' in the second and third trimester under the direction of other hormones produced in the later stages of pregnancy. At full term pregnancy, the stabilized cells result in mature breast tissue which will never again be as vulnerable to breast cancer.

Estrogen exposure is known to promote tumour growth. Induced abortion may independently increase the risk for breast cancer because of the tumour promoting effect of the considerably raised estrogen (oestradiol) concentrations in early pregnancy. At the same time, an abortion would deny a woman the benefit of the differentiating hormones during late pregnancy. As well, induced abortion may enhance the estrogen mediated proliferation of normal but primitive cells, resulting in the presence of more cells which are vulnerable to subsequent primary carcinogenesis. On the other hand, subnormal levels of maternal oestradiol are found to be the most reliable predictor of first trimester miscarriage (spontaneous abortion). Many retrospective studies have failed to distinguish between the physiology of spontaneous abortion and that of induced abortion.

In 1994 the National Cancer Institute funded an interview study of 1800 women over a seven year period. It focused specifically on induced abortion and breast cancer making the distinction between spontaneous and induced abortion and also addressed the issue of 'response bias'. The published results of the research of Janet R. Daling, Ph.D. et al of the Fred Hutchinson Cancer Research Centre, Seattle, Washington, instantly became an object of attack by the media, special interest groups and fellow researchers. Overall, the Daling study determined that women under age 45 who had an induced abortion had a 50% greater risk for developing breast cancer than did 'matched' women who had been pregnant at least once and never had an abortion. Among women who first terminated a pregnancy before age 18, the risk of breast cancer was 150 % higher. Among women who experienced an induced abortion after age 30, the risk was 110% higher.

At the Centre for Biostatistics and Epidemiology, Dept. of Pharmacology, Pennsylvania State University, Dr. Joel Brind Ph.D. and his research colleagues took two years to prepare a meta-analysis of the 23 independent and previously published international studies which made the distinction between spontaneous and induced abortion to determine whether induced abortion could be an independent factor for increasing a woman's risk of developing breast cancer. Their review appeared in the prestigious Journal of Epidemiology and Community Health - Great Britain, in October 1996. Dr. Brind's team used the records of over 60,000 women. They found a 30% increased risk for the development of breast cancer independent of any other factor except induced abortion. They found a 50% increased risk for the development of breast cancer if the abortion was done on a first pregnancy. The abortion/breast cancer link was demonstrated in white, Asian and black women. The data suggests that the risk is even greater for women with a family history of breast cancer, especially for those teenagers who may not be aware of their family history. The increased risk for developing breast cancer was seen in populations of different ethnicity, diet, socioeconomic and lifestyle patterns.

The research team expressed the hope that their meta-analysis would clarify directions for future research, eliminate any confusion regarding spontaneous vs. induced abortion and most significantly, it would ultimately help women contemplating an abortion to be fully informed of the risks for their health. They said, "...there exists the more present need for those in clinical practice to inform their patients fully about what is already known."

Women cannot control their family history, their environmental surroundings, the onset of menstruation or menopause or the aging process; however, induced abortion is an elective medical procedure which can be rejected in favour of other options. Legal abortion is never safe for children waiting to be born and it is not always safe for their mothers.


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Last modified on Thursday, 10 March 2022 15:53