title: 3D ultrasonography to evaluate fetal urinary production rates in twin gestation: construction of a normal value curve.
abstract: OBJECTIVE
  The aim of this study was to assess fetal urinary production rates (FUPR) in twin gestations using 3D ultrasonography with VOCAL® (virtual organ computer-aided analysis) and to develop a curve of normal values for the target population.
  
  
  METHODS
  A cross-sectional study was performed in 30 normal twin pregnancies with gestational ages ranging from 20 to 34 weeks. FUPR was measured using a three-dimensional ultrasound (3D US) virtual organ computer-aided analysis (VOCAL) system. FUPR (ml/hour) was calculated during the filling phase using the equation UPR = (VFB(2) - VFB(1))/time. The values for UPR were plotted as a function of fetal biometry (biparietal diameter) to generate a nomogram.
  
  
  RESULTS
  A total of 41 normal twin fetuses with gestational ages between 20 and 34 weeks were investigated. Eleven were excluded because of inadequate bladder contour image quality and/or the observation of micturition in one or both fetuses. Linear regression analysis of FUPR as a function of biparietal diameter (BPD) shows the normal range for UPR by fetal biometry and is expressed by the following equation: Ln(UPR) = -5.0121 + 0.0548 BPD (R(2) 0.3386, p value <.001). There was no statistically significant difference when the UPR was stratified by chorionicity.
  
  
  CONCLUSIONS
  The use of biometric parameters to predict fetal FUPR seems to be useful. In twin pregnancies, BPD is the variable that is most closely related to FUPR. For each 1 mm increase in BPD, there is a 5% increase in FUPR. Chorionicity did not affect FUPR.
authors: Grupo Perinatal, Rio de Janeiro, Brazil.
authors: Carolina Carvalho
authors: CC
authors: Mocarzel
authors: Department of Obstetrics, Hospital Servidores do Estado do Rio de Janeiro, Rio de Janeiro, Brazil.
authors: Renato Augusto Moreira
authors: RA
authors: de Sá
authors: Universidade Federal Fluminense, Rio de Janeiro, Brazil.
authors: Luis Guillermo Coca
authors: LG
authors: Velarde
authors: Grupo Perinatal, Rio de Janeiro, Brazil.
authors: Fernando Maia
authors: FM
authors: Peixoto-Filho
authors: Department of Obstetrics and Maternal-Fetal Medicine, Université Paris Descartes, Paris, France.
authors: Yves
authors: Y
authors: Ville
mesh_terms: D005260:Female; D005865:Gestational Age; D006801:Humans; D007091:Image Processing, Computer-Assisted; D011247:Pregnancy; D059285:Pregnancy, Twin; D012016:Reference Values; D014427:Twins; D016216:Ultrasonography, Prenatal; D001743:Urinary Bladder / Q000000981:diagnostic imaging*