title: Pregnancy outcome of monochorionic twins: does amnionicity matter?
abstract: OBJECTIVE
  To compare the fetal loss rate of monochorionic (MC) twin pregnancies according to their amnionicity.
  
  
  METHODS
  A retrospective review of all MC pregnancy outcomes in a tertiary centre. Pregnancy outcomes were compared for monochorionic monoamniotic (MCMA) versus monochorionic diamniotic (MCDA) pregnancies.
  
  
  RESULTS
  29 MCMA and 117 MCDA twin pregnancies were identified. The overall fetal loss rate was significantly higher in MCMA (23/52, 44.2%) compared to MCDA pregnancies (28/233, 12%, Chi squared = 30.03, p < .001). Kaplan-Meier analysis showed that fetal survival rate in MCDA twins were significantly higher than in MCMA twins (Log-rank Chi-squared = 27.9, p < .0005). Early pregnancy ultrasound identified the causes for these fetal losses in some MCMA twins. After exclusion of identifiable causes, the difference in fetal survival was not significant in the two groups (Log-rank chi-squared = 0.373, p = .54).
  
  
  CONCLUSIONS
  The loss rate for MCMA twins is high and occurs mainly due to discordant congenital abnormality, conjoint twins or twin reversed arterial perfusion (TRAP) sequence. Although the fetal loss rate in MCDA is lower than in MCMA pregnancies, the majority of fetal loss in MCDA pregnancies cannot be predicted at the first scan at presentation. The data of this study questions the widespread policy of a difference in the scheduling of elective delivery for MCMA and MCDA twins.
authors.affiliation: Fetal Medicine Unit, Academic Department of Obstetrics and Gynaecology, St George's University of London, United Kingdom.
authors.forename: Thiran
authors.initials: T
authors.lastname: Dias
authors.forename: Elena
authors.initials: E
authors.lastname: Contro
authors.forename: Basky
authors.initials: B
authors.lastname: Thilaganathan
authors.forename: Hina
authors.initials: H
authors.lastname: Khan
authors.forename: Cristina
authors.initials: C
authors.lastname: Zanardini
authors.forename: Samina
authors.initials: S
authors.lastname: Mahsud-Dornan
authors.forename: Amar
authors.initials: A
authors.lastname: Bhide
mesh_terms: D000328:Adult; D000650:Amnion / Q000378:metabolism*; D000653:Amniotic Fluid / Q000378:metabolism*; D005260:Female; D005865:Gestational Age; D006801:Humans; D053208:Kaplan-Meier Estimate; D011247:Pregnancy; D011256:Pregnancy Outcome; D059285:Pregnancy, Twin; D012189:Retrospective Studies; D013997:Time Factors; D055815:Young Adult