title: Communicating Down syndrome risk according to maternal age: "1-in-X" effect on perceived risk.
abstract: OBJECTIVE
  The appropriateness of the 1-in-X numerical format to convey quantitative medical probabilities is currently under discussion because of its distortive effect on subjective probability assessment. Previous research, however, always asked participants to imagine a hypothetical scenario. The aim of the present research is to support the existence of the 1-in-X effect in a real setting: when pregnant women have to evaluate their personal risk of Down syndrome according to their maternal age.
  
  
  METHODS
  During the first prenatal visit, pregnant women were asked to evaluate their own risk of having a child with Down syndrome according to their age, when such risk was presented either in the 1-in-X or in the N-in-NX format. Then, they were asked to assess their risk of having a child with Down syndrome.
  
  
  RESULTS
  Results showed a systematic higher risk assessment when pregnant women were presented with the 1-in-X format (mean = 3.57, standard deviation = 1.4) than with the N-in-NX format (mean = 3.03, standard deviation = 1.4), P = 0.007. Whereas the effect was shown to be not moderated by a differential comprehension of the two numerical formats, women with a low educational level and those who were at their first pregnancy were shown to be significantly more vulnerable.
  
  
  CONCLUSIONS
  The present findings corroborate the existence of the 1-in-X effect in a real-world setting, showing that, in pregnant women, the 1-in-X format actually elicits a higher perceived risk of Down syndrome, compared with the N-in-NX format.
authors.affiliation: Center for Experimental Research on Management and Economics, DCP, University IUAV of Venice, Venice, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Pighin
authors.affiliation: Department of Economics and Management, University of Trento, Trento, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Savadori
authors.affiliation: Department of Cognitive Science and Education, University of Trento, Trento, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Barilli
authors.affiliation: Unit of Genomic for the Diagnosis of Human Pathologies, Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Galbiati
authors.affiliation: Department of Obstetrics and Gynecology, San Raffaele Hospital, Milan, Italy.
authors.forename: Maddalene
authors.initials: M
authors.lastname: Smid
authors.affiliation: Unit of Genomic for the Diagnosis of Human Pathologies, Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, Milan, Italy.|Laboratory of Clinical Molecular Biology, IRCCS Ospedale San Raffaele, Milan, Italy.|Università Vita-Salute San Raffaele, Milan, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Ferrari
authors.affiliation: Unit of Genomic for the Diagnosis of Human Pathologies, Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Cremonesi
mesh_terms: D000293:Adolescent; D000328:Adult; D004314:Down Syndrome; D005260:Female; D006801:Humans; D008423:Maternal Age; D008875:Middle Aged; D010465:Perception; D011247:Pregnancy / Q000523:psychology*; D011295:Prenatal Care / Q000379:methods*; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D016037:Single-Blind Method; D055815:Young Adult