Induced abortion and breast cancer
BCPI FACT SHEET
Induced Abortion and Breast Cancer Risk
Induced abortion increases breast cancer risk.
If a woman has an induced abortion prior to 32 weeks but after 20 weeks, she has the same
vulnerability as a woman delivering prematurely before 32 weeks, because her breasts will not have
developed enough Type 4 lobules to protect her against breast cancer. If a woman has an induced
abortion before 20 weeks’ gestation, she will have the same vulnerability as a woman experiencing a
non-hormonal spontaneous abortion. Her breasts will have commenced proliferation of Type 1 and Type
2 (cancer-vulnerable) lobules but will not have experienced the protective processes that mitigate this
Long gestation before induced abortion increases breast cancer risk.
The longer a woman is pregnant before an induced abortion, the more cancer-vulnerable
Type 1 and Type 2 lobules she will develop, and the higher will be her risk for breast cancer.
Induced abortion increases risk of premature delivery.
When a woman gives birth naturally, it takes many hours to dilate the cervix. During an
abortion, the cervix is forcibly dilated and subjected to injury, and this damage to the cervix may cause a
woman to later have a premature delivery. Two large meta-analyses show that induced abortion
increases a woman’s risk of premature delivery.58 Furthermore, the more induced abortions a woman
has, the higher is her risk of subsequent premature births.59
This line of research led the Institutes of Medicine in 2006 to list induced abortion as an
“immutable” cause of increased risk of premature birth.60 As noted above, this increased likelihood to
deliver prematurely may affect a woman’s future breast health. For example: The breast cancer risk of a
woman whose first pregnancy ends in abortion and whose first birth occurs before 32 weeks’ gestation
(due to damage from her abortion) may actually be transiently increased, rather than decreased, by her
58 P. Shah and J. Zao, on behalf of Knowledge Synthesis Group of Determinants of Preterm/LBW Births, “Induced
Termination of Pregnancy and Low Birthweight and Preterm Birth: A Systematic Review and Meta-Analyses,” British Journal of
Obstetrics and Gynaecology 116, no. 11 (2009): 1425-1442; Hanes M. Swingle, Tarah T. Colaizy, M. Bridget Zimmerman, and
Frank H. Morriss, “Abortion and Risk of Subsequent Preterm Birth: A Systematic Review and Meta-Analyses,” Journal of
Reproductive Medicine 54 (2009): 95-108.
59 Brent Rooney and Byron C. Calhoun, “Induced Abortion and Risk of Later Premature Births,” Journal of American
Physicians and Surgeons 8, no. 2 (2003): 46-49.
60 Institute of Medicine, Committee on Understanding Premature Birth and Assuring Healthy Outcomes, Preterm
Birth: Causes, Consequences and Prevention, eds. Richard E. Behrman and Adrienne Stith Butler (2007), Appendix B, Table
5, 519; http://books.nap.edu/openbook.php? record_id=11622&page=625 (accessed January 16, 2013).
pages 1—133 of this paper can be read in their entirety by clicking on the following link:
http://www.bcpinstitute.org/papers/ILM_Vol 29_No1_1-133.pdf or by visiting the
Publications Page http://www.bcpinstitute.org/publishedpapers.htm on the BCPI website.
Taken with permission from ISSUES IN LAW & MEDICINE, “Breast Cancer and Induced Abortion: A Comprehensive Review
of Breast Development and Pathophysiology, the Epidemiologic Literature, and Proposal for Creation of Databanks to
Elucidate All Breast Cancer Risk Factors,” Vol. 29, No. 1, Spring 2014.
Angela E. Lanfranchi, M.D., FACS, and Patrick Fagan, Ph,D.