title: Screening for twin-twin transfusion syndrome at 11-14 weeks of pregnancy: the key role of ductus venosus blood flow assessment.
abstract: OBJECTIVE
  A discrepancy in crown-rump length (CRL) and/or nuchal translucency thickness (NT) between monochorionic twins has been found to be associated with an increased risk of twin-twin transfusion syndrome (TTTS). As one of the most plausible mechanisms for increased NT is hemodynamic imbalance and cardiac dysfunction, indirectly manifested by abnormal blood flow in the ductus venosus (DV), we aimed to clarify the role of DV blood flow assessment in identifying those monochorionic twins more prone to develop TTTS.
  
  
  METHODS
  We present 99 cases of monochorionic diamniotic twin pregnancies in which CRL, NT and DV blood flow were evaluated at 11-14 weeks' gestation.
  
  
  RESULTS
  Discrepant values of CRL were not predictive of TTTS development. Intertwin NT discrepancy >or= 0.6 mm had a sensitivity of 50.0% and a specificity of 92.0%. The presence of at least one abnormal blood flow waveform in the DV was associated with a relative risk for developing TTTS of 11.86 (95% CI, 3.05-57.45), with a sensitivity of 75.0% and a specificity of 92.0%. The combination of abnormal DV blood flow with NT discrepancy >or= 0.6 mm yielded a relative risk for the development of TTTS of 21 (95% CI, 5.47-98.33).
  
  
  CONCLUSIONS
  Both intertwin discrepancy in NT and abnormal flow in the DV in monochorionic twins may represent early manifestations of hemodynamic imbalance between donor and recipient. In these pregnancies, in addition to NT measurement at 11-14 weeks, the Doppler assessment of DV blood flow significantly increases the performance of screening for those at risk of developing TTTS.
authors.affiliation: Department of Obstetrics and Gynecology, Faculty of Medicine, Hospital of S. João, Porto, Portugal. almatias@mail.telepac.pt
authors.forename: A
authors.initials: A
authors.lastname: Matias
authors.forename: N
authors.initials: N
authors.lastname: Montenegro
authors.forename: T
authors.initials: T
authors.lastname: Loureiro
authors.forename: M
authors.initials: M
authors.lastname: Cunha
authors.forename: S
authors.initials: S
authors.lastname: Duarte
authors.forename: D
authors.initials: D
authors.lastname: Freitas
authors.forename: M
authors.initials: M
authors.lastname: Severo
mesh_terms: D001783:Blood Flow Velocity / Q000502:physiology; D018568:Crown-Rump Length; D005260:Female; D005318:Fetal Heart / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005330:Fetofetal Transfusion / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006801:Humans; D008099:Liver / Q000098:blood supply; D048208:Nuchal Translucency Measurement / Q000379:methods; D011247:Pregnancy; D011446:Prospective Studies; D014427:Twins; D016216:Ultrasonography, Prenatal; D014471:Umbilical Veins / Q000503:physiopathology*; D014682:Vena Cava, Inferior / Q000196:embryology / Q000503:physiopathology*