Abortion and Breast Cancer

Currently, scientists cannot agree about whether there is a link between abortion and breast cancer. Some studies have shown an association between induced abortion and breast cancer, while others have shown no link. Abortion is at least four times more prevalent than breast cancer so links that are made may not actually be due to a cause and effect relationship.

All of the studies that have been reported in reputable journals to date depend on the women accurately reporting their history of abortion. Many women may under report their history for all sorts of personal reasons; indeed it is estimated that 40% of women under report their past history of abortion. This means that the available studies have significant inconsistencies so that the results may not be true. In a Danish study of 1.5 million women, there was no association shown between induced abortion and breast cancer. This study relied on uniformly collected data in Danish registries thereby avoiding the major problem of differential reporting of abortions.

Studies that follow women through time, collecting information about women's health histories as it occurs need to be done before conclusions are drawn. These are called cohort studies; they are undertaken over many years so it may be several years before the actual risk is known.

It is also known that full term pregnancy before age 25 lowers breast cancer risk. Delaying having a full term pregnancy until later life means that the woman does not have the protective effect against breast cancer. Most pregnancies are delayed by women's use of contraception rather than abortion. All women who delay having full term pregnanct until after age 25 have an increased risk of breast cancer, so the risk is not just due to having an abortion. There are lots of other factors such as diet and family history that also affect a woman's chances of developing breast cancer.

Regular breast examinations, following a healthy diet with plenty of exercise and not smoking are all important ways of looking after your health.

REFERENCES

1. Brind J. et al. Induced abortion as an independent risk factor for breast cancer: a comprehensive review and meta-analysis. Journal of Epidemiology and Community Health 1996;50:481-496.

2. Melbye M et al. Induced abortion and the risk of breast cancer. New England Journal of Medicine 1997;336:81-85.

3. Henshaw S. Pregnancy termination and risk of breast cancer. JAMA 1996 276(1):31.

4. Michels K. et al. Abortion and breast cancer risk in seven countries. Cancer Causes and Control. 6(1):75-82, 1995 Jan.

5. Tavani A. et al. Abortion and breast cancer risk. International Journal of Cancer. 65(4):401-5, 1996 Feb 8.

6. Lipworth L. et al. Abortion and the risk of breast cancer; a case control in Greece. International Journal of Cancer. 61(2);181-4, 1995 Apr 10.

7. Palmer J. et al. Induced and spontaneous abortion in relation to breast cancer (United States). Cancer Causes and Control. 8(6):841-9, 1997 Nov.

8. Wingo P A. et al. The risk of breast cancer following spontaneous or induced abortion [review]. Cancer Causes and Control. 8(1); 93-108, 1997 Jan.

9. Newcomb P. et al. Pregnancy termination in relation to the risk of breast cancer. JAMA 275(4);283-87. 1996 Jan.

10. Gammon M. et al. Abortion and breast cancer: is there a believable association? [editorial]. JAMA 275(4);321-322.

11. Senghas R. Induced abortion and the risk of breast cancer. New England Journal of Medicine 336(25); 1834-1835 1997 June.

12. Andrieu N. et al. Familial risk, abortion and their interactive effect on the risk of breast cancer - a combined analysis of six case control studies. British Journal of Cancer. 72(3):744-51, 1995 Sep.