(Reaffirmed 2011, Replaces No. 285, August 2003)
This document reflects emerging clinical and scientific advances as of the date issued and is subject to change. The information should not be construed as dictating an exclusive course of treatment or procedure to be followed.
ABSTRACT: The relationship between induced abortion and the subsequent development of breast cancer has been the subject of a substantial amount of epidemiologic study. Early studies of the relationship between prior induced abortion and breast cancer risk were methodologically flawed. More rigorous recent studies demonstrate no causal relationship between induced abortion and a subsequent increase in breast cancer risk.
The relationship between induced abortion and the subsequent development of breast cancer has been the subject of a substantial amount of epidemiologic study. Early case– control studies that reported an association between induced abortion and subsequent development of breast cancer had significant methodological problems, most notably reliance on retrospective reporting of abortion history. A key methodological consideration in interpreting the evidence for any relationship between abortion and breast cancer risk is the sensitive nature of abortion, which could affect the accuracy in retrospective studies that rely on participant reports of having had an abortion.
In contrast to retrospective studies, prospective studies conclude there is no association between induced abortion and breast cancer. A world-wide meta-analysis of 83,000 women examined the relationship between induced abortion and breast cancer and found a significant difference between the overall estimate of relative risk (RR) from studies that had recorded information on induced abortion prospectively (RR, 0.93; 95% confidence interval, 0.89–0.96) and the overall estimate of RR from studies that had recorded such information retrospectively (RR, 1.11; 95% confidence interval, 1.09–1.14), suggesting that reporting bias was probably present in studies using retrospective reporting of abortion history (1).
In 2003, the National Cancer Institute convened the Early Reproductive Events and Breast Cancer Workshop to evaluate the current strength of evidence of epidemiologic, clinical, and animal studies addressing the association between reproductive events and the risk of breast cancer (2). The workshop participants concluded that induced abortion is not associated with an increase in breast cancer risk. Studies published since 2003 continue to support this conclusion (3–7).
Early studies of the relationship between prior induced abortion and breast cancer risk were methodologically flawed. More rigorous recent studies demonstrate no causal relationship between induced abortion and a subsequent increase in breast cancer risk.
- Beral V, Bull D, Doll R, Peto R, Reeves G. Breast cancer and abortion: collaborative reanalysis of data from 53 epidemiological studies, including 83,000 women with breast cancer from 16 countries. Collaborative Group on Hormonal Factors in Breast Cancer. Lancet 2004;363:1007–16.
- National Cancer Institute. Summary report: early reproductive events and breast cancer workshop. Bethesda (MD): NCI; 2003. Available at: http://www.cancer.gov/cancertopics/ ere-workshop-report. Retrieved November 6, 2008.
- Rosenblatt KA, Gao DL, Ray RM, Rowland MR, Nelson ZC, Wernli KJ, et al. Induced abortions and the risk of all cancers combined and site-specific cancers in Shanghai. Cancer Causes Control 2006;17:1275–80.
- Reeves GK, Kan SW, Key T, Tjonneland A, Olsen A, Overvad K, et al. Breast cancer risk in relation to abortion: results from the EPIC study. Int J Cancer 2006;119:1741–5.
- Michels KB, Xue F, Colditz GA, Willett WC. Induced and spontaneous abortion and incidence of breast cancer among young women: a prospective cohort study. Arch Intern Med 2007;167:814–20.
- Lash TL, Fink AK. Null association between pregnancy termination and breast cancer in a registry-based study of parous women. Int J Cancer 2004;110:443–8.
- Henderson KD, Sullivan-Halley J, Reynolds P, Horn-Ross PL, Clarke CA, Chang ET, et al. Incomplete pregnancy is not associated with breast cancer risk: the California Teachers Study. Contraception 2008;77:391–6.
Copyright © June 2009 by the American College of Obstetricians and Gynecologists, 409 12th Street, SW, PO Box 96920, Washington, DC 20090-6920. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, posted on the Internet, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher. Requests for authorization to make photocopies should be directed to: Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400.
Induced Abortion and Breast Cancer Risk. ACOG Committee Opinion No. 434. American College of Obstetricians and Gynecologists. Obstet Gynecol 2009;113:1417–8.