It has long been disputed among medical researchers that induced abortion (IA) puts women at a higher risk for breast cancer. A recent analysis revealed a 44% increased risk of breast cancer among females who had at least one induced abortion. The risk increased significantly for those who had 2 or more abortions.1 According to the American College of Pediatricians, this argument is supported by an increasing number of studies which show, “induced abortion (IA) to be linked to this rise. A plausible mechanism for that link is the interference by IA with normal breast cell maturation into cancer resistant cells.”2

 Put simply, the ductwork (or lobules) within a woman’s breasts develops in stages. The early stage of this ductwork consists of Type 1 and Type 2 lobules. These immature lobules are known to be more susceptible to cancer.

 During pregnancy, estrogen encourages the body to increase the number of Type 1 and Type 2 lobules. This rapid growth often causes breasts to feel sore or tender in early pregnancy. By week 32, the majority of those Type 1 and Type 2 lobules mature into Type 4 milk-producing lobules, which are significantly more cancer-resistant. However, interrupting pregnancy before 32 weeks, while Type 1 and Type 2 lobules are at an increased number but before they can mature into Type 4 lobules, puts a woman at increased risk for breast cancer.3

75% of a woman’s pre-pregnancy lobules are Type 1, where 80% of all breast cancers are formed. “Immature breast cells are particularly vulnerable to damage by carcinogens … from puberty to a woman’s first full term pregnancy.”4

Photo: Breast Cancer Prevention Institute

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1  Huang, Y., et al., (2014). A meta-analysis of the association between induced abortion and breast cancer risk among Chinese females. Cancer Causes Control; 25(2): 227-36.

2 American College of Pediatricians. (2019). Reproductive Choices of Young Women Affecting Future Breast Cancer Risk | American College of Pediatricians (acpeds.org)

3 Lanfranchi AE, Fagan P (2014). 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. Issues Law Med, 29(1).

4 Cornell University. Estrogen & Breast Cancer Risk: The Relationship. (1998). Reproductive Breast Cancer Risks Brochure (iinet.net.au)

Medically Reviewed By:

KATHY MAUER, BSN, RN

VP PATIENT SERVICES