title: The Effect of Breastfeeding Duration and Parity on the Risk of Epithelial Ovarian Cancer: A Systematic Review and Meta-analysis.
abstract: OBJECTIVE
  We conducted a systematic review and meta-analysis to summarize current evidence regarding the association of parity and duration of breastfeeding with the risk of epithelial ovarian cancer (EOC).
  
  
  METHODS
  A systematic search of relevant studies published by December 31, 2015 was performed in PubMed and EMBASE. A random-effect model was used to obtain the summary relative risks (RRs) and 95% confidence intervals (CIs).
  
  
  RESULTS
  Thirty-two studies had parity categories of 1, 2, and ≥3. The summary RRs for EOC were 0.72 (95% CI, 0.65 to 0.79), 0.57 (95% CI, 0.49 to 0.65), and 0.46 (95% CI, 0.41 to 0.52), respectively. Small to moderate heterogeneity was observed for one birth (p<0.01; Q=59.46; I2=47.9%). Fifteen studies had breastfeeding categories of <6 months, 6-12 months, and >13 months. The summary RRs were 0.79 (95% CI, 0.72 to 0.87), 0.72 (95% CI, 0.64 to 0.81), and 0.67 (95% CI, 0.56 to 0.79), respectively. Only small heterogeneity was observed for <6 months of breastfeeding (p=0.17; Q=18.79, I2=25.5%). Compared to nulliparous women with no history of breastfeeding, the joint effects of two births and <6 months of breastfeeding resulted in a 0.5-fold reduced risk for EOC.
  
  
  CONCLUSIONS
  The first birth and breastfeeding for <6 months were associated with significant reductions in EOC risk.
authors.affiliation: Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Ho Kyung
authors.identifier: 0000-0002-1207-0298
authors.initials: HK
authors.lastname: Sung
authors.affiliation: Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Korea.|Cancer Research Institute, Seoul National University, Seoul, Korea.
authors.forename: Seung Hyun
authors.initials: SH
authors.lastname: Ma
authors.affiliation: Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Korea.|Cancer Research Institute, Seoul National University, Seoul, Korea.|Department of Biomedical Science, Seoul National University Graduate School, Seoul, Korea.
authors.forename: Ji-Yeob
authors.initials: JY
authors.lastname: Choi
authors.affiliation: Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Korea.|Cancer Research Institute, Seoul National University, Seoul, Korea.|Department of Biomedical Science, Seoul National University Graduate School, Seoul, Korea.
authors.forename: Yunji
authors.initials: Y
authors.lastname: Hwang
authors.affiliation: Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Korea.|Cancer Research Institute, Seoul National University, Seoul, Korea.|Department of Biomedical Science, Seoul National University Graduate School, Seoul, Korea.
authors.forename: Choonghyun
authors.initials: C
authors.lastname: Ahn
authors.affiliation: Department of Obstetrics and Gynecology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Byoung-Gie
authors.initials: BG
authors.lastname: Kim
authors.affiliation: Department of Obstetrics and Gynecology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Yong-Man
authors.initials: YM
authors.lastname: Kim
authors.affiliation: Department of Obstetrics and Gynecology, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Jae Weon
authors.initials: JW
authors.lastname: Kim
authors.affiliation: Department of Gynecologic Oncology, National Cancer Center, Goyang, Korea.
authors.forename: Sokbom
authors.initials: S
authors.lastname: Kang
authors.affiliation: Division of Gynecologic Oncology, Department of Obstetrics and Gynecology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Jaehoon
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Obstetrics and Gynecology, Cheil General Hospital and Women's Healthcare Center, Kwandong University College of Medicine, Seoul, Korea.
authors.forename: Tae Jin
authors.initials: TJ
authors.lastname: Kim
authors.affiliation: Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Keun-Young
authors.initials: KY
authors.lastname: Yoo
authors.affiliation: Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Korea.|Cancer Research Institute, Seoul National University, Seoul, Korea.|Department of Biomedical Science, Seoul National University Graduate School, Seoul, Korea.
authors.forename: Daehee
authors.initials: D
authors.lastname: Kang
authors.affiliation: Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Korea.|Cancer Research Institute, Seoul National University, Seoul, Korea.|Department of Biomedical Science, Seoul National University Graduate School, Seoul, Korea.
authors.forename: Suekyung
authors.identifier: 0000-0001-5002-9707
authors.initials: S
authors.lastname: Park
mesh_terms: D019313:BRCA1 Protein / Q000235:genetics; D024682:BRCA2 Protein / Q000235:genetics; D001942:Breast Feeding; D000077216:Carcinoma, Ovarian Epithelial; D016208:Databases, Factual; D005260:Female; D006801:Humans; D009154:Mutation; D009375:Neoplasms, Glandular and Epithelial / Q000209:etiology*; D016017:Odds Ratio; D010051:Ovarian Neoplasms / Q000209:etiology*; D010298:Parity; D012306:Risk; D013997:Time Factors
chemical_list: D019313:BRCA1 Protein; D024682:BRCA2 Protein
keywords: Breast feeding; Meta-analysis; Ovarian neoplasms; Parity; Reproduction; Risk factors