TY - JOUR
T1 - Induced and spontaneous abortion and incidence of breast cancer among young women
T2 - A prospective cohort study
AU - Michels, Karin B.
AU - Xue, Fei
AU - Colditz, Graham A.
AU - Willett, Walter C.
PY - 2007/4/23
Y1 - 2007/4/23
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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=34247491518&partnerID=8YFLogxK
U2 - 10.1001/archinte.167.8.814
DO - 10.1001/archinte.167.8.814
M3 - Article
C2 - 17452545
AN - SCOPUS:34247491518
SN - 0003-9926
VL - 167
SP - 814
EP - 820
JO - Archives of internal medicine
JF - Archives of internal medicine
IS - 8
ER -