title: Ultrasound detection rate of single umbilical artery in the first trimester of pregnancy.
abstract: OBJECTIVE
  To determine accuracy of first trimester detection of single umbilical artery (SUA).
  
  
  METHODS
  The number of vessels in the umbilical cord was examined in a prospective cohort of 779 singleton, low-risk, unselected pregnancies, in the first (11-13 weeks) and second (17-24 weeks) trimesters, using both power and color Doppler and after delivery, by placental histopathologic exam. Concordance between first and second trimester findings to postnatal diagnoses was compared by calculating kappa coefficients.
  
  
  RESULTS
  There was medium concordance between the findings in the first trimester and the postnatal diagnoses (kappa = 0.52) and high concordance (kappa = 0.89) for the second trimester scan. Sensitivity, specificity, positive and negative predictive values for the findings in the first trimester were 57.1, 98.9, 50.0 and 99.2% and for the second trimester were 86.6, 99.9, 92.9 and 99.7%.
  
  
  CONCLUSIONS
  Sensitivity and positive predictive value of first trimester scan to identify an isolated SUA in a prospective unselected population was poor. Diagnosis of isolated SUA as well as a definitive judgment about the presence of associated anomalies would still require a scan in the second trimester.
authors.affiliation: Disciplina de Obstetrícia, do Departamento de Obstetrícia e Ginecologia, da Faculdade de Medicina, da Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Clarissa O
authors.initials: CO
authors.lastname: Lamberty
authors.forename: Mário Henrique Burlacchini
authors.initials: MH
authors.lastname: de Carvalho
authors.forename: Javier
authors.initials: J
authors.lastname: Miguelez
authors.forename: Adolfo Wenjaw
authors.initials: AW
authors.lastname: Liao
authors.forename: Marcelo
authors.initials: M
authors.lastname: Zugaib
mesh_terms: D000328:Adult; D018568:Crown-Rump Length; D005260:Female; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011262:Pregnancy Trimester, Second; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D058529:Single Umbilical Artery / Q000000981:diagnostic imaging*; D016216:Ultrasonography, Prenatal