title: Monochorionic twins with unequal placental sharing: why can the outcome still be favorable?
abstract: OBJECTIVE
  In monochorionic diamniotic (MCDA) twin pregnancies, unequal placental sharing does not always lead to adverse outcomes. The aim of this study is to investigate how unequal placental sharing may be compensated by placental anatomical changes.
  
  
  METHODS
  Between January 2012 and July 2013, a total of 60 uncomplicated MCDA pregnancies ending in live birth of healthy twins were studied. Placentas were divided into two groups; an equally shared placenta group (placenta territory discordance ≤ 25%, N = 40) and an unequally shared placenta group (placenta territory discordance >25%, N = 20). Angioarchitecture, cord insertion type and the distance between two cord insertions were compared.
  
  
  RESULTS
  Vascular anastomoses were seen in all 60 placentas, and 58 placentas (96.7%) had arterioarterial anastomoses (AA). The overall diameter of the AA was larger in the unequally shared placenta group as compared to the equally shared placentas (0.27 ± 0.12 cm versus 0.19 ± 0.1 cm, p < 0.05). The distance between the cord insertions was shorter in the unequally shared group (14.5 ± 6.0 cm versus 18.3 ± 6.5 cm, p < 0.05).
  
  
  CONCLUSIONS
  The absence of adverse outcomes in unequally shared placenta group can be explained by the presence of large AA and shorter distance between cord insertions, protecting the twin with the smaller placental part against growth restriction and other pathology.
authors.affiliation: a School of Public Health, Fudan University , Shanghai , P.R. China .|b Department of Obstetrics , Fetal Medicine Unit & Prenatal Diagnosis Center, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine , Shanghai , P.R. China .|c Department of Epidemiology and Social Science on Reproductive Health , Shanghai Institute of Planned Parenthood Research/WHO Collaborating Center on Human Reproduction , Shanghai , P.R. China .
authors.forename: Lu-Ming
authors.initials: LM
authors.lastname: Sun
authors.affiliation: b Department of Obstetrics , Fetal Medicine Unit & Prenatal Diagnosis Center, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine , Shanghai , P.R. China .
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.affiliation: b Department of Obstetrics , Fetal Medicine Unit & Prenatal Diagnosis Center, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine , Shanghai , P.R. China .
authors.forename: Gang
authors.initials: G
authors.lastname: Zou
authors.affiliation: b Department of Obstetrics , Fetal Medicine Unit & Prenatal Diagnosis Center, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine , Shanghai , P.R. China .
authors.forename: Fenghe
authors.initials: F
authors.lastname: Zhou
authors.affiliation: d Department of Neonatology , Affiliated Hospital of Luzhou Medical College , Luzhou , Sichuan , P.R. China .
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Lei
authors.affiliation: e Berry Genomics , Chaoyang District , Beijing , P.R. China , and.
authors.forename: David S
authors.initials: DS
authors.lastname: Cram
authors.affiliation: f Division of Fetal Medicine, Department of Obstetrics , Leiden University Medical Center , Leiden , The Netherlands.
authors.forename: Dick
authors.initials: D
authors.lastname: Oepkes
authors.affiliation: a School of Public Health, Fudan University , Shanghai , P.R. China .|c Department of Epidemiology and Social Science on Reproductive Health , Shanghai Institute of Planned Parenthood Research/WHO Collaborating Center on Human Reproduction , Shanghai , P.R. China .
authors.forename: Junqing
authors.initials: J
authors.lastname: Wu
mesh_terms: D000328:Adult; D001163:Arteriovenous Anastomosis / Q000473:pathology; D001724:Birth Weight; D004396:Coloring Agents; D005260:Female; D006801:Humans; D010920:Placenta / Q000098:blood supply* / Q000473:pathology*; D021041:Placental Circulation; D011247:Pregnancy; D059285:Pregnancy, Twin; D014430:Twins, Monozygotic; D014470:Umbilical Cord / Q000473:pathology
chemical_list: D004396:Coloring Agents
keywords: Monochorionic diamniotic; placental anastomoses; placental injection; uncomplicated