title: Biometrical threshold of biparietal diameter for certain fetal sex assignment by ultrasound.
abstract: OBJECTIVE
  The aim of this study was to establish the biometric threshold of biparietal diameter (BPD), assumed to be an independent variable of gestational age, at which 100% accuracy in the assessment of fetal sex by ultrasonography is achievable.
  
  
  METHODS
  Transvaginal and/or transabdominal sonography was used for detecting the 'sagittal sign' as a marker of fetal sex in 385 fetuses with BPD between 18 and 29 mm. The results of ultrasound examination were compared with sex at birth or with karyotype obtained from amniotic fluid cells or chorionic villus sampling.
  
  
  RESULTS
  Fetal sex assignment was feasible in 337 of 385 cases (87.5%). Of the 312 fetuses with known fetal sex outcome, 164 were males and 148 were females. An accuracy rate of 100% was achieved when a BPD of > or = 23 mm was obtained.
  
  
  CONCLUSIONS
  This study provides important information about the earliest stage of fetal development, expressed in terms of BPD, at which a diagnosis of fetal sex can be made with 100% accuracy.
authors.affiliation: Department of Obstetric Science, Modena University, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Mazza
authors.forename: G
authors.initials: G
authors.lastname: Contu
authors.forename: C
authors.initials: C
authors.lastname: Falcinelli
authors.forename: S
authors.initials: S
authors.lastname: Battafarano
authors.forename: A
authors.initials: A
authors.lastname: Cagnacci
authors.forename: G
authors.initials: G
authors.lastname: Vito
authors.forename: A
authors.initials: A
authors.lastname: Forabosco
authors.forename: A
authors.initials: A
authors.lastname: Volpe
mesh_terms: D001699:Biometry / Q000379:methods; D018568:Crown-Rump Length; D004056:Differential Threshold; D005260:Female; D005865:Gestational Age; D006801:Humans; D008297:Male; D010294:Parietal Bone / Q000000981:diagnostic imaging* / Q000196:embryology; D011237:Predictive Value of Tests; D012494:Sampling Studies; D012680:Sensitivity and Specificity; D012732:Sex Determination Analysis / Q000379:methods*; D016216:Ultrasonography, Prenatal