title: Placental characteristics in growth-discordant monochorionic twins: a matched case-control study.
abstract: OBJECTIVE
  To compare the placental characteristics in monochorionic (MC) twin pregnancies with and without birth weight discordance (BWD).
  
  
  METHODS
  We performed a matched case-control study to compare the placental characteristics of MC placentas from pregnancies with BWD (≥25%) (n = 47) with a control group of MC placentas without BWD (n = 47), matched for gestational age at birth. Placental sharing, angioarchitecture and diameter of the arterio-arterial (AA) anastomosis were assessed by placental injection with colored dye.
  
  
  RESULTS
  The rate of velamentous cord insertion in MC placentas with and without BWD was 30% (28/94) and 16% (15/94), respectively (p = 0.036). Placental sharing discordance in MC placentas with and without BWD was 36% and 17%, respectively (p < 0.001). The mean diameter of the AA anastomosis in MC placentas with and without BWD was 2.2 mm and 1.8 mm, respectively (p = 0.024).
  
  
  CONCLUSIONS
  MC placentas from growth-discordant twins are more unequally shared, have a higher rate of velamentous cord insertions and larger diameter of AA anastomosis compared to gestational age matched controls.
authors.affiliation: Division of Neonatology, Department of Pediatrics, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands. e.lopriore@lumc.nl
authors.forename: E
authors.initials: E
authors.lastname: Lopriore
authors.forename: S A
authors.initials: SA
authors.lastname: Pasman
authors.forename: F J
authors.initials: FJ
authors.lastname: Klumper
authors.forename: J M
authors.initials: JM
authors.lastname: Middeldorp
authors.forename: F J
authors.initials: FJ
authors.lastname: Walther
authors.forename: D
authors.initials: D
authors.lastname: Oepkes
mesh_terms: D001724:Birth Weight / Q000502:physiology; D016022:Case-Control Studies; D002823:Chorion; D004200:Diseases in Twins / Q000473:pathology; D005260:Female; D047109:Fetal Development / Q000502:physiology; D005317:Fetal Growth Retardation / Q000473:pathology*; D020567:Fetal Weight / Q000502:physiology; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D010920:Placenta / Q000473:pathology*; D010929:Placentation; D011247:Pregnancy; D059285:Pregnancy, Twin / Q000502:physiology; D014430:Twins, Monozygotic