title: Dichorionic twin ultrasound surveillance: sonography every 4 weeks significantly underperforms sonography every 2 weeks: results of the Prospective Multicenter ESPRiT Study.
abstract: OBJECTIVE
  A 2-week ultrasound scanning schedule for monochorionic twins is endorsed widely. There is a lack of robust data to inform a schedule for the surveillance of dichorionic gestations. We aimed to determine how ultrasound scanning that is performed at 2- or 4-week intervals (or every 4 weeks before 32 weeks' gestation and every 2 weeks thereafter) may impact the prenatal detection of fetal growth restriction (FGR) and ultimately influence timing of delivery.
  
  
  METHODS
  In a consecutive cohort of 789 dichorionic twin pregnancies that were recruited prospectively for the multicenter Evaluation of Sonographic Predictors of Restricted Growth in Twins study, ultrasound determination of fetal growth and interrogation of umbilical and middle cerebral artery Doppler scans were performed every 2 weeks from 24 weeks' gestation until delivery. Complete delivery and perinatal outcome data were recorded for all pregnancies. Where delivery was prompted by FGR, abnormal umbilical artery Doppler examination or poor biophysical profile and in the absence of ruptured membranes, onset of labor, preeclampsia, or antepartum hemorrhage, the delivery was considered "ultrasound-indicated." For ultrasound-indicated deliveries, detection probabilities for FGR/abnormal umbilical artery Doppler scans/poor biophysical were determined according to the interval between examinations, by the suppression if alternate examination data.
  
  
  RESULTS
  Among 789 dichorionic twin pregnancies, 66 pairs (8%) had an "ultrasound indicated" delivery. Detection of FGR was reduced from 88-69%, and detection of abnormal umbilical artery Doppler was reduced from 82-62% when a 4-week ultrasound schedule was simulated. Both of these reductions reached statistical significance. There was a nonsignificant trend toward a reduction in the recording of oligohydramnios with a 4-week interval between examinations.
  
  
  CONCLUSIONS
  This study suggests that the ultrasound surveillance program of every 2 weeks that is recommended currently for monochorionic twins should be extended to dichorionic gestations.
authors.affiliation: Department of Obstetrics and Gynecology, Rotunda Hospital, Dublin, Ireland. Electronic address: siobhancorcoran@rcsi.ie.
authors.forename: Siobhan
authors.initials: S
authors.lastname: Corcoran
authors.affiliation: Department of Obstetrics and Gynecology, Royal College of Surgeons in Ireland, Dublin, Ireland.
authors.forename: Fionnuala
authors.initials: F
authors.lastname: Breathnach
authors.affiliation: Department of Obstetrics and Gynecology, Graduate Entry Medical School, University of Limerick, Limerick, Ireland.
authors.forename: Gerard
authors.initials: G
authors.lastname: Burke
authors.affiliation: Department of Obstetrics and Gynecology, University College Dublin, Dublin, Ireland.
authors.forename: Fionnuala
authors.initials: F
authors.lastname: McAuliffe
authors.affiliation: Department of Obstetrics and Gynecology, Rotunda Hospital, Dublin, Ireland.
authors.forename: Michael
authors.initials: M
authors.lastname: Geary
authors.affiliation: Department of Obstetrics and Gynecology, Coombe Women and Infants University Hospital, Dublin, Ireland.
authors.forename: Sean
authors.initials: S
authors.lastname: Daly
authors.affiliation: Department of Obstetrics and Gynecology, University College Cork, Cork, Ireland.
authors.forename: John
authors.initials: J
authors.lastname: Higgins
authors.affiliation: Department of Obstetrics and Gynaecology, Royal Jubilee Maternity Hospital Belfast, Belfast, Ireland.
authors.forename: Alyson
authors.initials: A
authors.lastname: Hunter
authors.affiliation: National University of Ireland, Galway, Ireland.
authors.forename: John J
authors.initials: JJ
authors.lastname: Morrison
authors.affiliation: Department of Obstetrics and Gynecology, National Maternity Hospital, Dublin, Ireland.
authors.forename: Shane
authors.initials: S
authors.lastname: Higgins
authors.affiliation: Department of Obstetrics and Gynecology, National Maternity Hospital, Dublin, Ireland.
authors.forename: Rhona
authors.initials: R
authors.lastname: Mahony
authors.affiliation: Department of Obstetrics and Gynecology, Royal College of Surgeons in Ireland, Dublin, Ireland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Dicker
authors.affiliation: Department of Obstetrics and Gynecology, Royal College of Surgeons in Ireland, Dublin, Ireland.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Tully
authors.affiliation: Department of Obstetrics and Gynecology, Royal College of Surgeons in Ireland, Dublin, Ireland.
authors.forename: Fergal D
authors.initials: FD
authors.lastname: Malone
mesh_terms: D000328:Adult; D015331:Cohort Studies; D036861:Delivery, Obstetric / Q000379:methods; D005260:Female; D005317:Fetal Growth Retardation / Q000000981:diagnostic imaging*; D005333:Fetus / Q000098:blood supply*; D005865:Gestational Age; D006801:Humans; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging; D011247:Pregnancy; D011256:Pregnancy Outcome; D059285:Pregnancy, Twin; D011446:Prospective Studies; D013997:Time Factors; D018608:Ultrasonography, Doppler; D016216:Ultrasonography, Prenatal / Q000379:methods*; D014469:Umbilical Arteries / Q000000981:diagnostic imaging
keywords: dichorionic; twins; ultrasound scanning