title: Reference charts for fetal biometric parameters in twin pregnancies according to chorionicity.
abstract: OBJECTIVE
  The objective of this article is to determine reference values for fetal biometric parameters in twin pregnancies and to compare these values between monochorionic and dichorionic pregnancies.
  
  
  METHODS
  A retrospective cross-sectional study was conducted among 157 monochorionic and 176 dichorionic twin pregnancies between 14 and 38 weeks of gestation. Biometric measurements included the biparietal diameter (BPD), abdominal circumference (AC), femurs length (FL) and estimated fetal weight (EFW). To evaluate the correlation between biometric parameters and gestational age, polynomial regression models were created, with adjustments using the coefficient of determination (R(2) ). Comparison between monochorionic and dichorionic pregnancies was performed using analysis of covariance.
  
  
  RESULTS
  The mean BPD, AC, FL and EFW for the dichorionic pregnancies were 56.16 mm, 191.1 mm, 41.08 mm and 816.1 g, respectively. The mean BPD, AC, FL and EFW for the monochorionic pregnancies were 57.14 mm, 184.2 mm, 39.29 mm and 723.4 g, respectively. There was a statistical difference between mono and dichorionic pregnancies for all the biometric parameters (BPD p = 0.012; AC p = 0.047; FL p = 0.007; EFW p = 0.011).
  
  
  CONCLUSIONS
  Reference curves of biometric parameters in twin pregnancies were determined. Biometric parameters were statistically different between monochorionic and dichorionic pregnancies.
authors.affiliation: Referral Center for Teaching of Diagnostic Imaging (CETRUS), São Paulo, SP, Brazil; Department of Obstetrics, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil.
authors.forename: Edward
authors.initials: E
authors.lastname: Araujo Júnior
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Ruano
authors.forename: Pouya
authors.initials: P
authors.lastname: Javadian
authors.forename: Wellington P
authors.initials: WP
authors.lastname: Martins
authors.forename: Julio
authors.initials: J
authors.lastname: Elito
authors.forename: Claudio Rodrigues
authors.initials: CR
authors.lastname: Pires
authors.forename: Sebastião Marques
authors.initials: SM
authors.lastname: Zanforlin Filho
mesh_terms: D000328:Adult; D002823:Chorion / Q000033:anatomy & histology*; D003430:Cross-Sectional Studies; D005260:Female; D047109:Fetal Development; D020567:Fetal Weight; D005333:Fetus / Q000033:anatomy & histology*; D005865:Gestational Age; D006801:Humans; D009929:Organ Size; D011247:Pregnancy; D059285:Pregnancy, Twin; D012016:Reference Values; D012189:Retrospective Studies; D014427:Twins; D016216:Ultrasonography, Prenatal; D055815:Young Adult