title: Doppler assessment of the uterine circulation in the second trimester in twin pregnancies: prediction of pre-eclampsia, fetal growth restriction and birth weight discordance.
abstract: OBJECTIVE
  To compare singleton nomograms of the uterine circulation with previously established twin nomograms in the prediction of pre-eclampsia, fetal growth restriction (FGR), and birth weight discordance > or = 20% in twin gestations.
  
  
  METHODS
  This was a retrospective analysis of maternal and perinatal data obtained from 256 dichorionic twin pregnancies. The mean uterine artery resistance index was calculated from both sides and the presence and absence of notching was recorded. Cut-off levels for abnormal flow parameters were the 95th centile of reference ranges of either singleton or twin nomograms.
  
  
  RESULTS
  According to twin reference values, 14.0% of patients were screen positive, compared to only 3.1% when singleton reference values were used. The sensitivity of abnormal uterine artery Doppler results defined by twin nomograms vs. singleton nomograms was 36.4% vs. 18.2% for pre-eclampsia, 26.7% vs. 9.7% for FGR, 28.9% vs. 7.9% for birth weight discordance > or = 20%, and 26.5% vs. 10.3% for any adverse outcome, respectively.
  
  
  CONCLUSIONS
  Despite using specially constructed twin nomograms, uterine artery Doppler studies in twin gestations had an overall low sensitivity in predicting adverse obstetric outcome. Negative predictive values of uterine Doppler studies in twin gestations are lower compared to those reported in unselected singleton pregnancies, i.e. maternal and fetal complications occur more frequently despite normal uterine artery waveforms. This suggests that there is an additional pathomechanism, causing pre-eclampsia and FGR in twin gestations, that is unrelated to uteroplacental insufficiency.
authors.affiliation: Department of Obstetrics and Gynecology, Division of Prenatal Medicine, University Medical School Bonn, Germany. annegeipel@hotmail.com
authors.forename: A
authors.initials: A
authors.lastname: Geipel
authors.forename: C
authors.initials: C
authors.lastname: Berg
authors.forename: U
authors.initials: U
authors.lastname: Germer
authors.forename: A
authors.initials: A
authors.lastname: Katalinic
authors.forename: M
authors.initials: M
authors.lastname: Krapp
authors.forename: J
authors.initials: J
authors.lastname: Smrcek
authors.forename: U
authors.initials: U
authors.lastname: Gembruch
mesh_terms: D000328:Adult; D005260:Female; D005317:Fetal Growth Retardation / Q000000981:diagnostic imaging*; D005320:Fetal Macrosomia / Q000000981:diagnostic imaging*; D006801:Humans; D011225:Pre-Eclampsia / Q000000981:diagnostic imaging*; D011237:Predictive Value of Tests; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011272:Pregnancy, Multiple; D012016:Reference Values; D012189:Retrospective Studies; D014427:Twins; D018608:Ultrasonography, Doppler / Q000379:methods*; D016216:Ultrasonography, Prenatal / Q000379:methods*; D014599:Uterus / Q000098:blood supply*