title: Influence of chorionicity on perinatal outcome in a large cohort of Danish twin pregnancies.
abstract: OBJECTIVE
  To assess outcome in twin pregnancies according to chorionicity.
  
  
  METHODS
  A cohort was retrieved from local ultrasound databases at 14 obstetric departments in Denmark, comprising all twin pregnancies with two live fetuses scanned between weeks 11 and 14 in the period 1 January 2004 to 31 December 2006. Outcome data were retrieved from the National Board of Health.
  
  
  RESULTS
  Among 2038 twin pregnancies, 1757 (86.2%) were dichorionic (DC) and 281 (13.8%) were monochorionic diamniotic (MC). In MC pregnancies, the rate of spontaneous fetal loss in both second and third trimesters was more than threefold higher than the comparable rate in DC pregnancies: 6.0% vs. 1.9% for at least one fetus in the second trimester (P < 0.001) and 2.1% vs. 0.7% in the third trimester (P = 0.03). In 98.4% of DC pregnancies and in 91.1% of MC pregnancies, at least one infant was liveborn. Amongst pregnancies with two live fetuses at 24 weeks, the proportion with two live infants at 28 days after delivery was 97.5% and 95.1%, respectively.
  
  
  CONCLUSIONS
  The increased incidence of fetal loss in MC pregnancies compared with DC pregnancies predominantly occurs before 24 weeks' gestation. After this stage, although the risk of intrauterine fetal death is still higher in MC than in DC pregnancies, if both fetuses are alive at 24 weeks, the chance of a woman having two live infants 1 month after delivery is similar in MC and DC pregnancies.
authors.affiliation: Department of Fetal Medicine, Copenhagen University Hospital, Copenhagen, Denmark. anna.oldenburg@gmail.com
authors.forename: A
authors.initials: A
authors.lastname: Oldenburg
authors.forename: L
authors.initials: L
authors.lastname: Rode
authors.forename: B
authors.initials: B
authors.lastname: Bødker
authors.forename: V
authors.initials: V
authors.lastname: Ersbak
authors.forename: A
authors.initials: A
authors.lastname: Holmskov
authors.forename: F S
authors.initials: FS
authors.lastname: Jørgensen
authors.forename: H
authors.initials: H
authors.lastname: Larsen
authors.forename: T
authors.initials: T
authors.lastname: Larsen
authors.forename: L
authors.initials: L
authors.lastname: Laursen
authors.forename: H
authors.initials: H
authors.lastname: Mogensen
authors.forename: O B
authors.initials: OB
authors.lastname: Petersen
authors.forename: S
authors.initials: S
authors.lastname: Rasmussen
authors.forename: L
authors.initials: L
authors.lastname: Skibsted
authors.forename: L
authors.initials: L
authors.lastname: Sperling
authors.forename: I
authors.initials: I
authors.lastname: Stornes
authors.forename: H
authors.initials: H
authors.lastname: Zingenberg
authors.forename: A
authors.initials: A
authors.lastname: Tabor
mesh_terms: D000328:Adult; D002823:Chorion / Q000000981:diagnostic imaging* / Q000473:pathology; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D005313:Fetal Death / Q000000981:diagnostic imaging* / Q000473:pathology; D005315:Fetal Diseases / Q000000981:diagnostic imaging* / Q000401:mortality / Q000473:pathology; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D054238:Perinatal Mortality; D011247:Pregnancy; D011256:Pregnancy Outcome; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014427:Twins; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D016216:Ultrasonography, Prenatal / Q000379:methods