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Induced abortion and the risk of breast cancer.
N Engl J Med. 1997 Jan 09; 336(2):81-5.NEJM

Abstract

BACKGROUND

It has been hypothesized that an interrupted pregnancy might increase a woman's risk of breast cancer because breast cells could proliferate without the later protective effect of differentiation.

METHODS

We established a population-based cohort with information on parity and vital status consisting of all Danish women born from April 1, 1935, through March 31, 1978. Through linkage with the National Registry of Induced Abortions, information on the number and dates of induced abortions among those women was combined with information on the gestational age of each aborted fetus. All new cases of breast cancer were identified through linkage with the Danish Cancer Registry.

RESULTS

In the cohort of 1.5 million women (28.5 million person-years), we identified 370,715 induced abortions among 280,965 women (2.7 million person-years) and 10,246 women with breast cancer. After adjustment for known risk factors, induced abortion was not associated with an increased risk of breast cancer (relative risk, 1.00; 95 percent confidence interval, 0.94 to 1.06). No increases in risk were found in subgroups defined according to age at abortion, parity, time since abortion, or age at diagnosis of breast cancer. The relative risk of breast cancer increased with increasing gestational age of the fetus at the time of the most recent induced abortion: <7 weeks, 0.81 (95 percent confidence interval, 0.58 to 1.13); 7 to 8 weeks, 1.01 (0.89 to 1.14); 9 to 10 weeks, 1.00 >12 weeks, 1.38 (1.00 to 1.90) (reference category, 9 to 10 weeks).

CONCLUSIONS

Induced abortions have no overall effect on the risk of breast cancer.

Links

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Authors+Show Affiliations

Melbye M
Department of Epidemiology Research, Danish Epidemiology Science Center, Statens Serum Institut, Copenhagen, Denmark.
Wohlfahrt J
No affiliation info available
Olsen JH
No affiliation info available
Frisch M
No affiliation info available
Westergaard T
No affiliation info available
Helweg-Larsen K
No affiliation info available
Andersen PK
No affiliation info available

MeSH

Abortion, InducedAdolescentAdultBreast NeoplasmsCase-Control StudiesChildDenmarkFemaleFollow-Up StudiesGestational AgeHumansMiddle AgedPregnancyRegistriesReproductive HistoryRiskRisk Factors

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

8988884

Citation

Melbye, M, et al. "Induced Abortion and the Risk of Breast Cancer." The New England Journal of Medicine, vol. 336, no. 2, 1997, pp. 81-5.
Melbye M, Wohlfahrt J, Olsen JH, et al. Induced abortion and the risk of breast cancer. N Engl J Med. 1997;336(2):81-5.
Melbye, M., Wohlfahrt, J., Olsen, J. H., Frisch, M., Westergaard, T., Helweg-Larsen, K., & Andersen, P. K. (1997). Induced abortion and the risk of breast cancer. The New England Journal of Medicine, 336(2), 81-5.
Melbye M, et al. Induced Abortion and the Risk of Breast Cancer. N Engl J Med. 1997 Jan 9;336(2):81-5. PubMed PMID: 8988884.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Induced abortion and the risk of breast cancer. AU - Melbye,M, AU - Wohlfahrt,J, AU - Olsen,J H, AU - Frisch,M, AU - Westergaard,T, AU - Helweg-Larsen,K, AU - Andersen,P K, PY - 1997/1/9/pubmed PY - 1997/1/9/medline PY - 1997/1/9/entrez KW - Abortion, Induced KW - Biology KW - Breast Cancer--determinants KW - Cancer KW - Denmark KW - Developed Countries KW - Diseases KW - Europe KW - Family Planning KW - Fertility Control, Postconception KW - Neoplasms KW - Northern Europe KW - Research Report KW - Risk Factors KW - Scandinavia SP - 81 EP - 5 JF - The New England journal of medicine JO - N Engl J Med VL - 336 IS - 2 N2 - BACKGROUND: It has been hypothesized that an interrupted pregnancy might increase a woman's risk of breast cancer because breast cells could proliferate without the later protective effect of differentiation. METHODS: We established a population-based cohort with information on parity and vital status consisting of all Danish women born from April 1, 1935, through March 31, 1978. Through linkage with the National Registry of Induced Abortions, information on the number and dates of induced abortions among those women was combined with information on the gestational age of each aborted fetus. All new cases of breast cancer were identified through linkage with the Danish Cancer Registry. RESULTS: In the cohort of 1.5 million women (28.5 million person-years), we identified 370,715 induced abortions among 280,965 women (2.7 million person-years) and 10,246 women with breast cancer. After adjustment for known risk factors, induced abortion was not associated with an increased risk of breast cancer (relative risk, 1.00; 95 percent confidence interval, 0.94 to 1.06). No increases in risk were found in subgroups defined according to age at abortion, parity, time since abortion, or age at diagnosis of breast cancer. The relative risk of breast cancer increased with increasing gestational age of the fetus at the time of the most recent induced abortion: <7 weeks, 0.81 (95 percent confidence interval, 0.58 to 1.13); 7 to 8 weeks, 1.01 (0.89 to 1.14); 9 to 10 weeks, 1.00 >12 weeks, 1.38 (1.00 to 1.90) (reference category, 9 to 10 weeks). CONCLUSIONS: Induced abortions have no overall effect on the risk of breast cancer. SN - 0028-4793 UR - https://www.unboundmedicine.com/medline/citation/8988884/Induced_abortion_and_the_risk_of_breast_cancer_ L2 - https://www.nejm.org/doi/10.1056/NEJM199701093360201?url_ver=Z39.88-2003&amp;rfr_id=ori:rid:crossref.org&amp;rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -