title: Association between abortion and breast cancer: an updated systematic review and meta-analysis based on prospective studies.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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).
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  The current prospective evidences are not sufficient to support the positive association between abortion (including IA and SA) and breast cancer risk.
authors.affiliation: Department of Oncology, Dongfeng Hospital, Hubei University of Medicine, No. 10, Daling Road, Shiyan, 442008, Hubei, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Guo
authors.forename: Yubei
authors.initials: Y
authors.lastname: Huang
authors.forename: Lei
authors.initials: L
authors.lastname: Yang
authors.forename: Zhengqiang
authors.initials: Z
authors.lastname: Xie
authors.forename: Shuhong
authors.initials: S
authors.lastname: Song
authors.forename: Juan
authors.initials: J
authors.lastname: Yin
authors.forename: Li
authors.initials: L
authors.lastname: Kuang
authors.forename: Wengang
authors.initials: W
authors.lastname: Qin
mesh_terms: D000028:Abortion, Induced / Q000009:adverse effects*; D000328:Adult; D001943:Breast Neoplasms / Q000209:etiology*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D010298:Parity; D011247:Pregnancy; D011446:Prospective Studies; D012307:Risk Factors