title: Are the first trimester volumetric measurements with two dimensional ultrasonography satisfactory?
abstract: OBJECTIVE
  Aim was to examine volumetric measurement of first trimester structures with two-dimensional ultrasonography (2D US) and evaluate necessity of three-dimensional (3D) volume measurements instead of 2D during first trimester.
  
  
  METHODS
  Using 2D transvaginal ultrasound imaging, the crown rump length (CRL), yolk sac (YS) and gestational sac (GS) diameters were recorded in 176 women with gestational age <11 weeks. Volume measurements were done by using a simplified formula for the volume of a prolate ellipsoid: V = 0.523 × length × height × width.
  
  
  RESULTS
  The mean CRL value was 19.6 ± 8.8 mm. The mean YS, GS and embrionic volume (EV) varied from 0.02-0.13, 5.5-37.72, 0.024-3.31 cm(3) between 6(+6) and 10(+6) weeks, respectively. There was moderate positive correlation between EV versus GS volume and YS volume versus EV.
  
  
  CONCLUSIONS
  2D US still can provide adequate information in volumetric examination of regular shaped objects. But 3D US is useful in volumetric measurements of irregular shaped structures and for screening of fetal abnormalities.
authors.affiliation: Department of Obstetrics and Gynecology, Fatih University, Faculty of Medicine, Ankara, Turkey.
authors.forename: Aydin
authors.initials: A
authors.lastname: Köşüş
authors.forename: Nermin
authors.initials: N
authors.lastname: Köşüş
authors.forename: Nilgün Ö
authors.initials: NÖ
authors.lastname: Turhan
mesh_terms: D000328:Adult; D005260:Female; D058746:Gestational Sac / Q000000981:diagnostic imaging*; D006801:Humans; D021621:Imaging, Three-Dimensional; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011446:Prospective Studies; D012016:Reference Values; D016216:Ultrasonography, Prenatal / Q000592:standards*; D015017:Yolk Sac / Q000000981:diagnostic imaging*