title: Reporting Down syndrome screening results: women's understanding of risk.
abstract: OBJECTIVE
  To compare women's understanding of different methods of expressing Down syndrome risks.
  
  
  METHODS
  A self-administered structured questionnaire given to 311 English-speaking women postpartum, at three maternity units. Understanding of numeric risk expression was assessed by women identifying whether a specified risk was higher, lower or the same as another nominated risk, expressed as two percentages, as two ratios or one of each. Perceptions of a high-risk result were obtained using display rankings of percentages and ratios.
  
  
  RESULTS
  Response rate was 95% (294/311). Overall, women were poor comparing numeric risks whether expressed similarly (ratio vs. ratio or percentage vs. percentage) or not. When comparing similarly expressed risks, 66% (95% CI: 62-70%) of respondents were correct, considerably more than when asked to compare different risk expressions 30% (95% CI: 26-34%), P < 0.0001. Women were more tolerant of risk when expressed as a percentage than as a ratio (median high risk for percentage form was 5% (1:20) and for ratio form was 1:200 (0.5%).
  
  
  CONCLUSIONS
  Women's understanding of Down syndrome risk is dependent upon how risks are expressed. These findings may usefully direct how risk should be reported to women having prenatal screening for Down syndrome.
authors.affiliation: Department of Obstetrics and Gynaecology, Centre for Women's Health Research, Monash Institute of Medical Research, Monash University, Australia.
authors.forename: Cate
authors.initials: C
authors.lastname: Nagle
authors.forename: Ryan
authors.initials: R
authors.lastname: Hodges
authors.forename: Rory
authors.initials: R
authors.lastname: Wolfe
authors.forename: Euan M
authors.initials: EM
authors.lastname: Wallace
mesh_terms: D000293:Adolescent; D000328:Adult; D003625:Data Collection; D004314:Down Syndrome / Q000175:diagnosis*; D005260:Female; D005817:Genetic Counseling; D007722:Health Knowledge, Attitudes, Practice; D006801:Humans; D011247:Pregnancy; D011296:Prenatal Diagnosis; D012306:Risk; D055815:Young Adult