title: Sonography interval and the diagnosis of twin-twin transfusion syndrome.
abstract: OBJECTIVE
  To evaluate the relationship between sonography surveillance interval and Quintero stage at diagnosis.
  
  
  METHODS
  This was a retrospective cohort study of monochorionic diamniotic pregnancies diagnosed with twin-twin transfusion syndrome (TTTS) and followed with serial sonography between 1997 and 2013. Women were divided into three cohorts: diagnosis at initial second-trimester sonogram, at a sonogram within 14 d of the prior exam, and at a sonogram greater than 14 d from the prior exam. Isolated amniotic fluid abnormalities were also recorded.
  
  
  RESULTS
  TTTS was identified in 48 pregnancies, with 50% of cases diagnosed at the initial sonogram, 21% within 14 d of a prior sonogram, and 29% more than 14 d from a prior sonogram. There was no association between interval and TTTS stage at diagnosis. Of 24 cases diagnosed during a follow-up sonogram, 46% had an isolated amniotic fluid abnormality preceding diagnosis. When isolated oligohydramnios (29%) or hydramnios (17%) was present, the sonography interval was significantly shorter (p = 0.003), but no difference in TTTS stage at diagnosis was found.
  
  
  CONCLUSIONS
  Although frequent surveillance of monochorionic diamniotic pregnancies is prudent, when close follow-up of isolated fluid abnormalities was practiced, we were unable to demonstrate an effect of surveillance interval on stage of TTTS at diagnosis.
authors.affiliation: a Department of Obstetrics and Gynecology , The University of Texas Southwestern Medical Center , Dallas , TX , USA.
authors.forename: Elaine L
authors.initials: EL
authors.lastname: Duryea
authors.affiliation: a Department of Obstetrics and Gynecology , The University of Texas Southwestern Medical Center , Dallas , TX , USA.
authors.forename: Sarah K
authors.initials: SK
authors.lastname: Happe
authors.affiliation: a Department of Obstetrics and Gynecology , The University of Texas Southwestern Medical Center , Dallas , TX , USA.
authors.forename: Donald D
authors.initials: DD
authors.lastname: McIntire
authors.affiliation: a Department of Obstetrics and Gynecology , The University of Texas Southwestern Medical Center , Dallas , TX , USA.
authors.forename: Jodi S
authors.initials: JS
authors.lastname: Dashe
mesh_terms: D000328:Adult; D005260:Female; D005330:Fetofetal Transfusion / Q000000981:diagnostic imaging*; D005865:Gestational Age; D006801:Humans; D016104:Oligohydramnios / Q000000981:diagnostic imaging; D006831:Polyhydramnios / Q000000981:diagnostic imaging; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D059285:Pregnancy, Twin; D012189:Retrospective Studies; D013997:Time Factors; D014430:Twins, Monozygotic; D016216:Ultrasonography, Prenatal / Q000379:methods*; D055815:Young Adult
keywords: Monochorionic twins; sonography; twin–twin transfusion syndrome