title: [Early transvaginal sonographic measurement of cephalic index].
abstract: BACKGROUND
  The aim of this study is to obtain normal values of cephalic index by transvaginal scan early in pregnancy.
  
  
  METHODS
  In this prospective cross-sectional study, transvaginal high-resolution sonography was performed between 57 and 112 days' gestation in 1087 euploid fetuses. Measurements of cephalic index with standard deviations, calculated as the ratio biparietal diameter/occipito-frontal diameter, were obtained in the single gestational periods considered.
  
  
  RESULTS
  Cephalic index was found to show fairly constant values throughout the period evaluated with smaller values of standard deviation. The best correlation with gestational age was described by a linear correlation.
  
  
  CONCLUSIONS
  The data obtained by transvaginal scan can be used as parameters of normal values in early pregnancy.
mesh_terms: D002508:Cephalometry / Q000379:methods*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D011247:Pregnancy; D011446:Prospective Studies; D016216:Ultrasonography, Prenatal
vernacular_title: Misurazione dell'indice cefalico fetale in epoca precoce di gravidanza mediante ecografia transvaginale.