title: First trimester screening for holoprosencephaly with choroid plexus morphology ('butterfly' sign) and biparietal diameter.
abstract: OBJECTIVE
  The aim of this study was to determine whether choroid plexus morphology ('butterfly' sign) and biparietal diameter (BPD) are effective sonographic screening tools for holoprosencephaly (HPE) in the first trimester.
  
  
  METHODS
  An axial view of the fetal head was obtained routinely to determine the presence of the 'butterfly' sign in pregnancies presenting for sonographic screening at 11-13 weeks of gestation. The same view was also used to obtain BPD measurements. The definitive diagnosis of HPE was established by the sonographic demonstration of an anterior cerebral monoventricular cavity and thalamic fusion.
  
  
  RESULTS
  During a 9-year study period, 11 068 live fetuses were screened. There were 11 cases of HPE (prevalence 1/1006); all of them were detected by demonstration of an absent 'butterfly' sign with no false-positive cases. The BPD was less than the 5th percentile in 40% of the cases.
  
  
  CONCLUSIONS
  The 'butterfly' sign appears to be a highly sensitive marker for HPE in the first trimester. On the other hand, BPD measurements had a lower sensitivity, implying that microcephaly is not a prominent first-trimester feature in these cases. Incorporation of the 'butterfly' sign into the first trimester anatomy scan is simple and can facilitate the identification of the vast majority of fetuses with HPE in the first trimester.
authors.affiliation: Fetal Medicine Center, Department of Obstetrics and Gynecology, Clinica Las Condes, Santiago, Chile.
authors.forename: Waldo
authors.initials: W
authors.lastname: Sepulveda
authors.forename: Amy E
authors.initials: AE
authors.lastname: Wong
mesh_terms: D000293:Adolescent; D000328:Adult; D001837:Body Weights and Measures; D002677:Chile / Q000453:epidemiology; D002831:Choroid Plexus / Q000002:abnormalities / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D005260:Female; D006257:Head / Q000000981:diagnostic imaging; D016142:Holoprosencephaly / Q000000981:diagnostic imaging* / Q000453:epidemiology; D006801:Humans; D008875:Middle Aged; D010296:Parietal Lobe / Q000002:abnormalities / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D015995:Prevalence; D016216:Ultrasonography, Prenatal / Q000706:statistics & numerical data; D055815:Young Adult