title: Timing of menarche, childbearing and hysterectomy risk.
abstract: OBJECTIVE
  To examine the associations of age at menarche, timing of first birth and parity with hysterectomy rates; to investigate whether these associations were independent of each other and other potential confounders and varied by reason for hysterectomy.
  
  
  METHODS
  Women from the Medical Research Council National Survey of Health and Development, a cohort followed prospectively since birth in March 1946 across England, Scotland and Wales, were studied. Survival analyses were used to assess the relationships between reproductive characteristics and hysterectomy.
  
  
  RESULTS
  Age at menarche was inversely associated with hysterectomy rates (adjusted Hazard Ratio for hysterectomy associated with a 1 year increase in menarche=0.85 (95% CI: 0.77-0.95)). Parity was also associated with hysterectomy; women with > or =3 children experienced higher rates of hysterectomy than women with 1-2 children, who themselves experienced higher rates than nulliparous women. The associations of parity and age at menarche with hysterectomy were independent of each other and potential confounders. The association between age at menarche and hysterectomy was stronger for hysterectomies performed for fibroids than for other reasons.
  
  
  CONCLUSIONS
  Our findings suggest that age at menarche is most likely acting to influence hysterectomy risk through its association with lifetime oestrogen exposure whereas parity is most likely acting through an effect on decision-making processes. This highlights the importance of considering both biological and social pathways to hysterectomy and confirms that medical need is not the only factor which needs to be considered when making treatment decisions for gynaecological problems.
authors.affiliation: MRC Unit for Lifelong Health and Ageing, London, UK. r.cooper@nshd.mrc.ac.uk
authors.forename: Rachel
authors.initials: R
authors.lastname: Cooper
authors.forename: Rebecca
authors.initials: R
authors.lastname: Hardy
authors.forename: Diana
authors.initials: D
authors.lastname: Kuh
mesh_terms: D015331:Cohort Studies; D005260:Female; D006306:Health Surveys; D006801:Humans; D007044:Hysterectomy; D008423:Maternal Age; D008572:Menarche; D008875:Middle Aged; D016017:Odds Ratio; D010298:Parity; D011177:Postal Service; D011247:Pregnancy; D016016:Proportional Hazards Models; D006113:United Kingdom