title: First-trimester screening for chromosomal abnormalities by fetal nuchal translucency in a Brazilian population.
abstract: OBJECTIVE
  To examine the detection rate of chromosomal abnormalities using nuchal translucency (NT) thickness in a Brazilian population.
  
  
  METHODS
  This was a prospective study of 2996 singleton pregnancies with a live fetus at 10-14 weeks of gestation attending for routine antenatal care in a teaching hospital in Brazil. Fetal crown-rump length (CRL) and NT thickness were measured and the risks for trisomy 21 were calculated by a combination of maternal age and fetal NT with the use of software provided by The Fetal Medicine Foundation. Sensitivity and positive predictive values for different risk cut-offs were calculated.
  
  
  RESULTS
  Chromosomal defects were diagnosed in 22 cases, including 10 cases of trisomy 21. The estimated risk based on maternal age and fetal NT was 1 in 300 or greater in 222 (7.4%) cases and these included nine of 10 (90.0%) pregnancies with trisomy 21 and nine of 12 (75.0%) pregnancies with other chromosomal defects. The NT was above the 95th centile in 5.8% of cases and this group included 70% of the trisomy 21 cases.
  
  
  CONCLUSIONS
  A combination of maternal age and fetal NT provides an effective method of screening for chromosomal defects. The performance of the test in a Brazilian population is similar to that in Britain.
authors.affiliation: Department of Obstetrics, Hospital das Clínicas, Faculdade de Medicina da Universidade de São Paulo, Rua Dr Enéas de Carvalho Aguiar, 255, São Paulo, SP 05403-000 Brazil. mlbrizot@uol.com.br
authors.forename: M L
authors.initials: ML
authors.lastname: Brizot
authors.forename: M H
authors.initials: MH
authors.lastname: Carvalho
authors.forename: A W
authors.initials: AW
authors.lastname: Liao
authors.forename: N S
authors.initials: NS
authors.lastname: Reis
authors.forename: E
authors.initials: E
authors.lastname: Armbruster-Moraes
authors.forename: M
authors.initials: M
authors.lastname: Zugaib
mesh_terms: D001938:Brazil / Q000453:epidemiology; D025063:Chromosome Disorders / Q000000981:diagnostic imaging; D018568:Crown-Rump Length; D004314:Down Syndrome / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D008423:Maternal Age; D009333:Neck / Q000196:embryology*; D011237:Predictive Value of Tests; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011446:Prospective Studies; D012307:Risk Factors; D012680:Sensitivity and Specificity; D016216:Ultrasonography, Prenatal