title: Past obstetric history and risk of ovarian cancer.
abstract: BACKGROUND
  Early age at menarche and late age at last menstrual period, as well as other reproductive factors, may be the cause of development of some types of cancer concerning the female reproductive organs. It has been estimated that late menopause may be responsible for the occurrence of even 16% of cases of ovarian cancer in the population. The incidence of ovarian cancer is also higher among nulliparous women, and among those who rarely become pregnant.
  
  
  OBJECTIVE
  The objective of the study was analysis of the effect of reproductive factors on the risk of ovarian cancer.
  
  
  METHODS
  The study covered healthy women, without the diagnosis of focal lesions in the ovaries, and women with the diagnosis of ovarian cancer. The study was conducted during the period from September 2007-November 2011, and covered a total number of 1,346 women. Odds ratio was calculated for individual risk factors. Statistical analysis was performed by means of the statistical packages STATISTICA v8, GrafPad Instat v 3.00, Analyse-it v. 2.2, and Cytel Studio StatXact-8. Statistical hypothesis were verified on the level of significance p ≤ 0.05.
  
  
  RESULTS
  Among females who began menstruating by the age of 11, the risk of ovarian cancer was 1.6 higher than among those in whom the first period occurred at the age of over 13. Similarly, among women who menstruated at the age of over 55 the risk of development of ovarian cancer was 1.4 times higher. The age at which a woman delivered her first live baby is also of importance. In the group of women who gave birth at the age of over 35, the risk was elevated and remained on the level of OR=1.7; 95%CI 0.66-4.5, compared to those who bore the first baby under the age of 25. If the pregnancy was terminated with miscarriage, the risk of contracting ovarian cancer decreases, and was on the level of OR=0.8; 95%CI 0.53-1.28, compared to the women who have never been pregnant. Among patients who did not breastfeed their babies, ovarian cancer risk was 1.7 times higher, compared to those breastfeeding.
  
  
  CONCLUSIONS
  Reproductive factors exert a significant effect of the risk of development of ovarian cancer.
authors.affiliation: Department of Mother's and Child's Health, University of Medical Sciences, Poznan, Poland. bpieta@gpsk.am.poznan.pl
authors.forename: Beata
authors.initials: B
authors.lastname: Pięta
authors.forename: Karolina
authors.initials: K
authors.lastname: Chmaj-Wierzchowska
authors.forename: Tomasz
authors.initials: T
authors.lastname: Opala
mesh_terms: D000328:Adult; D000367:Age Factors; D005260:Female; D006801:Humans; D008875:Middle Aged; D016017:Odds Ratio; D010051:Ovarian Neoplasms / Q000453:epidemiology* / Q000209:etiology; D011044:Poland / Q000453:epidemiology; D011247:Pregnancy; D017584:Reproductive History; D012307:Risk Factors; D011795:Surveys and Questionnaires