Article

Induced and spontaneous abortion and incidence of breast cancer among young women - A prospective cohort study

Department of Nutrition , Harvard University, Cambridge, Massachusetts, United States
Archives of Internal Medicine (Impact Factor: 13.25). 05/2007; 167(8):814-20. DOI: 10.1001/archinte.167.8.814
Source: PubMed

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

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    ABSTRACT: Although positive association between abortion and breast cancer was frequently reported from case-control studies, results from prospective studies were still unclear. This study aimed to evaluate this association based on prospective studies. PubMed, ISI Web of Knowledge and Embase were systematically searched for prospective studies on the association between abortion and breast cancer up to April 2014, supplemented by manual searches on the references. Two reviewers independently conducted the literature search, study selection, data extraction, and quality assessment of included studies. Random effects models were used to estimate the combined relative risks (RRs) and corresponding 95 % confidence intervals (95 % CIs). Fifteen prospective studies [14 focused on induced abortion (IA), and 12 focused on spontaneous abortion (SA)] were included in the final analysis. The combined RRs (95 % CIs) of breast cancer risk were 1.00 (0.94-1.05) [1.00 (0.92-1.08) for cumulative-incidence data and 1.00 (0.94-1.05) for incidence-rate data] for IA, and 1.02 (0.95-1.09) [1.06 (0.96-1.16) for cumulative-incidence data and 1.01 (0.92-1.09) for incidence-rate data] for SA, respectively. Non-significant associations of breast cancer with IA and SA were also found among nulliparous women, women with abortion before or after the first full-term pregnancy, women with one or ≥2 abortions, and women with first abortion after 30 years old. The current prospective evidences are not sufficient to support the positive association between abortion (including IA and SA) and breast cancer risk.
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    • "Childbearing is acknowledged as protective against breast cancer, but the results of epidemiologic study on breast cancer in relation to abortions are inconsistent (Remennick, 1990; Daling et al., 1994; Brind et al., 1996; Newcomb et al., 1996; Ye et al., 2002; Beral et al., 2004; Palmer, et al., 2004; Brewster et al., 2005; Michels et al., 2007; Naieni et al., 2007; Ozmen et al., 2009). However, induced abortion have been widely used in China, to investigate the potential role of induced and spontaneous abortions as risk factors for the future development of breast cancer in Jiangsu' women of China, we conducted a case-control study. "
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    ABSTRACT: To evaluate the relationship between abortions and risk of breast cancer, we conducted a case-control study with 669 cases and 682 population-based controls in Jiangsu Province of China. A structured questionnaire was used to elicit detailed information. Unconditional logistic regression analysis was performed to calculate odds ratios (ORs) and 95% confidence intervals (CIs). The results have revealed that induced abortion was related to increased risk of breast cancer. Premenopausal women who had ≥ 3 times of induced abortion were at increased crude OR (2.41, 95%CI: 1.09-5.42) and adjusted-OR (1.55, 95%CI: 1.15-5.68). Postmenopausal women with a previous induced abortion were at increased crude OR (2.04, 95%CI: 1.48-2.81) and adjusted-OR (1.82, 95%CI: 1.30-2.54), and there was a significant increase trend in OR with number of induced abortions (p for trend: 0.0001). Overall, spontaneous abortion did not significantly alter the risk of breast cancer, but postmenopausal women who had history of spontaneous abortion were at increased OR. These results suggested that relationship between breast cancer and abortions may depend on menopausal status and induced abortion may played an important role in the development of breast cancer in Jiangsu' women of China.
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