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Induced and spontaneous abortion and incidence of breast cancer among young women: a prospective cohort study.
Arch Intern Med. 2007 Apr 23; 167(8):814-20.AI

Abstract

BACKGROUND

Induced abortion has been inconsistently associated with breast cancer risk in case-control studies. Retrospective cohort studies using registry information in Scandinavia have not suggested an increase in the incidence of breast cancer, although data on individual reproductive factors were not accounted for.

METHODS

We examined the association between induced and spontaneous abortion and the incidence of breast cancer in a prospective cohort of young women, the Nurses' Health Study II. The study included 105 716 women 29 to 46 years old at the start of follow-up in 1993. Information on induced or spontaneous abortions was collected in 1993 and updated biennially. During 973 437 person-years of follow-up between 1993 and 2003, 1458 newly diagnosed cases of invasive breast cancer were ascertained.

RESULTS

A total of 16 118 participants (15%) reported a history of induced abortion, and 21 753 (21%) reported a history of spontaneous abortions. The hazard ratio for breast cancer among women who had 1 or more induced abortions was 1.01 (95% confidence interval, 0.88-1.17) after adjustment for established breast cancer risk factors; among women with 1 or more spontaneous abortions, the covariate-adjusted hazard ratio was 0.89 (95% confidence interval, 0.78-1.01). The relation between induced abortion and the incidence of breast cancer did not differ materially by number of abortions (P for trend = .98), age at abortion (P for trend = .68), parity (P for interaction = .54), or timing of abortion with respect to a full-term pregnancy (P for interaction = .10).

CONCLUSION

Among this predominantly premenopausal population, neither induced nor spontaneous abortion was associated with the incidence of breast cancer.

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Authors+Show Affiliations

Michels KB
Obstetrics and Gynecology Epidemiology Center, Department of Obstetrics and Gynecology, Brigham and Women's Hospital, Harvard Medical School, Boston, Mass 02115, USA.
Xue F
No affiliation info available
Colditz GA
No affiliation info available
Willett WC
No affiliation info available

MeSH

Abortion, InducedAbortion, SpontaneousAdultAge FactorsBreast NeoplasmsCohort StudiesFemaleHumansMiddle AgedParityPregnancyProspective StudiesRisk Factors

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural

Language

eng

PubMed ID

17452545

Citation

Michels, Karin B., et al. "Induced and Spontaneous Abortion and Incidence of Breast Cancer Among Young Women: a Prospective Cohort Study." Archives of Internal Medicine, vol. 167, no. 8, 2007, pp. 814-20.
Michels KB, Xue F, Colditz GA, et al. Induced and spontaneous abortion and incidence of breast cancer among young women: a prospective cohort study. Arch Intern Med. 2007;167(8):814-20.
Michels, K. B., Xue, F., Colditz, G. A., & Willett, W. C. (2007). Induced and spontaneous abortion and incidence of breast cancer among young women: a prospective cohort study. Archives of Internal Medicine, 167(8), 814-20.
Michels KB, et al. Induced and Spontaneous Abortion and Incidence of Breast Cancer Among Young Women: a Prospective Cohort Study. Arch Intern Med. 2007 Apr 23;167(8):814-20. PubMed PMID: 17452545.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Induced and spontaneous abortion and incidence of breast cancer among young women: a prospective cohort study. AU - Michels,Karin B, AU - Xue,Fei, AU - Colditz,Graham A, AU - Willett,Walter C, PY - 2007/4/25/pubmed PY - 2007/5/18/medline PY - 2007/4/25/entrez SP - 814 EP - 20 JF - Archives of internal medicine JO - Arch Intern Med VL - 167 IS - 8 N2 - BACKGROUND: Induced abortion has been inconsistently associated with breast cancer risk in case-control studies. Retrospective cohort studies using registry information in Scandinavia have not suggested an increase in the incidence of breast cancer, although data on individual reproductive factors were not accounted for. METHODS: We examined the association between induced and spontaneous abortion and the incidence of breast cancer in a prospective cohort of young women, the Nurses' Health Study II. The study included 105 716 women 29 to 46 years old at the start of follow-up in 1993. Information on induced or spontaneous abortions was collected in 1993 and updated biennially. During 973 437 person-years of follow-up between 1993 and 2003, 1458 newly diagnosed cases of invasive breast cancer were ascertained. RESULTS: A total of 16 118 participants (15%) reported a history of induced abortion, and 21 753 (21%) reported a history of spontaneous abortions. The hazard ratio for breast cancer among women who had 1 or more induced abortions was 1.01 (95% confidence interval, 0.88-1.17) after adjustment for established breast cancer risk factors; among women with 1 or more spontaneous abortions, the covariate-adjusted hazard ratio was 0.89 (95% confidence interval, 0.78-1.01). The relation between induced abortion and the incidence of breast cancer did not differ materially by number of abortions (P for trend = .98), age at abortion (P for trend = .68), parity (P for interaction = .54), or timing of abortion with respect to a full-term pregnancy (P for interaction = .10). CONCLUSION: Among this predominantly premenopausal population, neither induced nor spontaneous abortion was associated with the incidence of breast cancer. SN - 0003-9926 UR - https://www.unboundmedicine.com/medline/citation/17452545/Induced_and_spontaneous_abortion_and_incidence_of_breast_cancer_among_young_women:_a_prospective_cohort_study_ L2 - https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/10.1001/archinte.167.8.814 DB - PRIME DP - Unbound Medicine ER -