title: Fetal biometry: size and configuration of the third ventricle.
abstract: OBJECTIVE
  To evaluate the normal configuration and size of the third ventricle in second and third trimester fetuses in a normal population, and to compare our values with those of previously published studies.
  
  
  METHODS
  Evaluation of fetal third ventricular width and configuration was obtained by antenatal ultrasonography in 474 fetuses with gestational age between 12 weeks and term (mean 28 weeks). Percentiles for third ventricle width were estimated by combining separate fractional polynominal regression models fitted to the mean and standard deviation, assuming that the measurements had a normal distribution at each gestational age. Appearance of the third ventricle was correlated with each gestational age.
  
  
  RESULTS
  The third ventricle could be visualized in 471 (99%) of 474 fetuses. The 97th percentile of the third ventricle in preterm fetuses was measured as 3.6 mm in size. The third ventricle was seen as a single echogenic line in 153 (32.4%) of 474 fetuses. Two-hundred-and-ninety-nine (61.5%) of all fetuses had parallel echogenic lines outlining a fluid-filled lumen. V-shaped third ventricular configuration was seen in only 28 (5.9%) of the fetuses. From 24 weeks to term, parallel echogenic lines were the most commonly (83.7% to 79.6%) encountered configuration for the third ventricle.
  
  
  CONCLUSIONS
  The 97th percentile of the third ventricle in preterm fetuses was measured as 3.6 mm in size. In the early second trimester, 77% of the fetuses had a single echogenic line appearance on ultrasonography. As the brain and ventricular structures mature, a parallel echogenic line becomes the prominent ultrasonography appearance (>80% of fetuses) in third trimester healthy fetuses.
authors.affiliation: KTU Farabi Hospital, Department of Radiology, 61080 Trabzon, Turkey.
authors.forename: A
authors.initials: A
authors.lastname: Sari
authors.forename: A
authors.initials: A
authors.lastname: Ahmetoglu
authors.forename: H
authors.initials: H
authors.lastname: Dinc
authors.forename: A
authors.initials: A
authors.lastname: Saglam
authors.forename: U
authors.initials: U
authors.lastname: Kurtoglu
authors.forename: S
authors.initials: S
authors.lastname: Kandemir
authors.forename: H Reşit
authors.initials: HR
authors.lastname: Gümele
mesh_terms: D000328:Adult; D001699:Biometry; D005260:Female; D047109:Fetal Development; D005333:Fetus / Q000033:anatomy & histology*; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third; D020542:Third Ventricle / Q000000981:diagnostic imaging / Q000196:embryology*; D016216:Ultrasonography, Prenatal