Abortion and Breast Cancer Policy

Preamble

The Australian Women’s Health Network recognises that there is controversy about whether induced abortion increases the risk of breast cancer but that the best available evidence indicates that induced abortion does not increase a woman’s risk of breast cancer later in life.

Policy

The Australian Women’s Health Network believes that continual public claims of any association between breast cancer and abortion are without factual basis and such claims only serve to cause unnecessary distress amongst women who suffer from breast cancer and others who have experienced an abortion. Current epidemiological evidence does not suggest any increased risk of breast cancer associated with induced abortion.

Rationale

  1. The World Health Organisation in its Fact Sheet No 240 in June 2000[1], concluded that induced abortion in the first trimester of pregnancy does not have the effect of raising a woman’s risk of developing breast cancer later in life.
  2. Recent guidelines from the College of Obstetricians and Gynaecologists in the United Kingdom state that the evidence about induced abortion and breast cancer is inconclusive but that, when only those studies least susceptible to bias are considered, there is no evidence that induced abortion increases the risk of breast cancer.
  3. A number of epidemiological studies have examined a possible relationship between breast cancer and abortion but the results have been inconsistent, with some studies showing an increased risk and some showing no effect or a protective effect. Most of the studies have been case control studies in which women with breast cancer and a control group of women without breast cancer have been interviewed and asked about their reproductive history.  While some of these studies claim to have shown a small increase in risk of breast cancer among women who have had an induced abortion, they are flawed because of problems with recall or reporting bias.  There is evidence that women with breast cancer are more likely than women in the control group to tell the interviewer if they have had an induced abortion.  This leads to an overestimation of the effect of induced abortion. Further, the results have not always taken into account the effect of other related risk factors such as age at first birth, use of the contraceptive pill or smoking behaviours.
  4. More recently there have been some large prospective cohort studies (in which the information about induced abortion is collected before the appearance of breast cancer) and studies based on linkage of independent records from registries. These cohort and record linkage studies are not subject to reporting bias and none of these studies have shown a statistically significant increase in breast cancer risk after exposure to induced abortion[2].

The Australian Women’s Health Network affirms its support of the principle and practice of medical practitioners ensuring that patients are resourced to enable them to provide informed consent to any medical treatment, including termination of pregnancy.

March 2002
www.awhn.org.au

[1] http://www.who.int/inf-fs/en/fact240.html (reproduced in Appendix 1)

[2] Lindefors-Harris BM, Eklund G, Meirik O, Rutqvist LE, Wiklund K  Risk of cancer of the breast after legal abortion during first trimester: a Swedish register study.  BMJ 1989;299:1430-2; Melbye M, Wohlfahrt J, Olsen JH, et al.  Induced abortion and the risk of breast cancer.  New England Journal of Medicine 1997;336:81-5; Goldacre MJ.  Kurina LM.  Seagroatt V.  Yeates D.  Abortion and breast cancer: a case-control record linkage study. Journal of Epidemiology & Community Health.  55(5):336-7, 2001 May; Bartholomew LL.  Grimes DA. The alleged association between induced abortion and risk of breast cancer: biology or bias?. Obstetrical & Gynecological Survey.  53(11):708-14, 1998 Nov.

APPENDIX 1

WORLD HEALTH ORGANISATION
Fact Sheet No 240
June 2000

INDUCED ABORTION DOES NOT INCREASE THE RISK OF BREAST CANCER

Breast cancer: Cancer of the breast is common in developed countries where the lifetime risk ranges from 1 in 12 to 1 in 20 women. Among women living in developing countries the risk is lower but appears to be increasing. Risk factors for breast cancer include high socio-economic status, early menarche, late first birth, late menopause, and a family history of breast cancer.

Induced abortion: Currently, in countries where induced abortion is permitted by law, which have total fertility rates of about 2 or less and high prevalence rates of contraceptive use, the annual rate of induced abortion is 1 to 2 abortions per 100 women of reproductive age. In these countries on average, almost every second woman has an abortion during her life. In countries with similar fertility rates but much lower prevalence of contraceptive use, the annual rate of induced abortion is higher and can be estimated to be up to 10 or more per 100 women annually. In countries where abortion is permitted by the law, the large majority of abortions (typically > 90%) take place before the end of the 12th week of pregnancy.

Risk of breast cancer following induced abortion: Most of the information on whether induced abortion modifies the risk of breast cancer among women comes fromepidemiological studies, which are either case-control studies, or historical cohort studies. For information on abortion, all published case-control studies have relied on interviews of cases and controls with the inherent problem of recall bias. This bias occurs because women with breast cancer (cases) tend to truthfully report induced abortion while controls, who often are healthy women, have no “incentive” to provide information about personal and sensitive matters such as induced abortion. Such bias can produce elevated relative risk estimates in case-control studies. As a result, the outcome of such studies has been inconsistent, with some having indicated a small increase in risk, while others have not.

Historical cohort studies, on the other hand, are more methodologically sound. Two major studies have been carried out using this methodology, and neither found an increased risk of breast cancer associated with first trimester abortion.

Therefore, results from epidemiological studies are reassuring in that they show no consistent effect of first trimester induced abortion upon a woman’s risk of breast cancer later in life.

Further reading

  1. Lindefors-Harris B-M et al. American Journal of Epidemiology 1991;134:1003-8.
  2. Daling et al. Journal of the National Cancer Institute 1994;86:1584-92.
  3. Brind et al. Journal of Epidemiology and Community Health 1996;50:481-96
  4. Meirik et al. Journal of Epidemiology and Community Health 1998;52:209-11
  5. Lindefors Harris B-M et al. British Medical Journal 1989;299:1430-2
  6. Melbye M et al. New England Journal of Medicine 1997;336:81-5
  7. Daling et al. American Journal of Epidemiology 1996;144:373-80
  8. McCredie M et al. International Journal of Cancer 1998:76:182-88.
  9. Bartholomew LL and Grimes DA. Obstetric and Gynaecological Survey 1998;53:708-14.
  10. Blettner et al. Journal of Epidemiology and Community Health 1997;51:465