title: Risk of a Down syndrome live birth in women 45 years of age and older.
abstract: OBJECTIVE
  To determine the risk of a Down syndrome (DS) live birth for women 45 years of age and over.
  
  
  METHODS
  A meta-analysis of data from five published articles, 13 EUROCAT congenital anomaly population registers and two unpublished sources.
  
  
  RESULTS
  Information was available on the number of DS live births occurring amongst 13,745 live births to women 45 years of age and over. Information was also available on DS pregnancies diagnosed prenatally that were subsequently terminated. These pregnancies were adjusted for expected fetal loss to estimate the number of live births that would have occurred in the absence of prenatal diagnoses, when a total of 471 DS live births were estimated to have occurred. The risk of a DS birth did not increase for women 45 years of age and over. The average risk was 34 per 1000 births (95% CI: 31-37).
  
  
  CONCLUSIONS
  The risk of a DS live birth for women 45 years of age and over is considerably lower than has often been previously assumed. The most likely explanation is that women of this age are more likely to miscarry DS pregnancies than younger mothers.
authors.affiliation: Centre for Environmental and Preventive Medicine, Wolfson Institute of Preventive Medicine, Barts and The London School of Medicine and Dentistry, London, UK. j.k.morris@qmul.ac.uk
authors.forename: J K
authors.initials: JK
authors.lastname: Morris
authors.forename: C
authors.initials: C
authors.lastname: De Vigan
authors.forename: D E
authors.initials: DE
authors.lastname: Mutton
authors.forename: E
authors.initials: E
authors.lastname: Alberman
mesh_terms: D000328:Adult; D000649:Amniocentesis; D004314:Down Syndrome / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology*; D005060:Europe / Q000453:epidemiology; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008423:Maternal Age; D008875:Middle Aged; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology*; D012307:Risk Factors