title: Assessment of yolk sac volume by 3D-sonography using the XI VOCAL method from 7 to 10 + 6 weeks of pregnancy.
abstract: OBJECTIVE
  To access the yolk sac (YS) volume between 7 and 10 + 6 gestational weeks of pregnancy by threedimensional (3D) ultrasonography using extended imaging virtual organ computer-aided analysis (XI VOCAL) method.
  
  
  METHODS
  For this cross-sectional study, 64 pregnant patients between 7 and 10 + 6 gestational weeks were enrolled and normal pregnancies were included. The XI VOCAL 10 slices manual method was used for the YS volumetry by 3D ultrasonography. The statistical analysis first obtained the means, medians, standard deviation, and maximum and minimum volume values. The correlation of YS volume to the gestational age (GA) and the crown-rump length (CRL) was evaluated by models of polynomial regression, being adjusted by determination coefficient (R (2)).
  
  
  RESULTS
  The mean YS estimated volume ranged from 0.06 ± 0.03 cm(3) [0.02-0.11 cm(3)] to 0.16 ± 0.12 cm(3) [0.01-0.38 cm(3)] and showed to be weakly correlated to the GA [YS volume = exp(0.261 × GA + 0.008); R (2) = 0.14] and the CRL [YS volume = exp(0.033 × CRL + 0.035); R (2) = 0.13].
  
  
  CONCLUSIONS
  The YS volume estimated by 3D ultrasonography using the method XI VOCAL correlated weakly with GA and CRL in normal singleton pregnancies between 7 and 10 + 6 gestational weeks.
authors.affiliation: Department of Obstetrics, São Paulo Federal University (UNIFESP), Rua Carlos Weber, 950 apto. 113 Visage, Alto da Lapa, São Paulo, SP, CEP 05303-000, Brazil. araujojred@terra.com.br
authors.forename: Edward
authors.initials: E
authors.lastname: Araujo Júnior
authors.forename: Luciano Marcondes Machado
authors.initials: LM
authors.lastname: Nardozza
authors.forename: Liliam Cristine
authors.initials: LC
authors.lastname: Rolo
authors.forename: Karina Krajden
authors.initials: KK
authors.lastname: Haratz
authors.forename: Antonio Fernandes
authors.initials: AF
authors.lastname: Moron
mesh_terms: D003430:Cross-Sectional Studies; D005260:Female; D005865:Gestational Age; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D011247:Pregnancy; D012044:Regression Analysis; D016216:Ultrasonography, Prenatal / Q000379:methods*; D015017:Yolk Sac / Q000000981:diagnostic imaging*