title: Deep-hidden anastomoses in monochorionic twin placentae are harmless.
abstract: OBJECTIVE
  Our objective was to identify the clinical consequences of deep-hidden anastomoses that occur underneath the placental surface.
  
  
  METHODS
  Twelve placentae that underwent intrauterine laser ablation of placental anastomoses for twin-twin transfusion syndrome (TTTS) and 14 non-TTTS controls were investigated for deep-hidden anastomoses. Additionally, we investigated the inter-twin haemoglobin differences as an indicator for fetofetal transfusion. Placentae were divided into four groups: TTTS placentae without residual chorionic-plate anastomoses without deep-hidden anastomoses (group 1) and with deep-hidden anastomoses (group 2), and non-TTTS placentae with chorionic-plate anastomoses without deep-hidden anastomoses (group 3) and with deep-hidden anastomoses (group 4).
  
  
  RESULTS
  Deep-hidden anastomoses were identified in 58% (7/12) of the TTTS placentae after laser surgery and in 64% (9/14) of the non-TTTS placentae. Groups 1 and 2 had equal inter-twin haemoglobin differences: medians 1.4 and 1.2 gr/dL, respectively (p = 0.48). In group 3, the median inter-twin haemoglobin difference without deep-hidden anastomoses was 2.6 gr/dL (group 3) and with deep-hidden anastomoses (group 4) it was 5.1 gr/dL (p = 0.26).
  
  
  CONCLUSIONS
  Both comparisons imply that deep-hidden anastomoses did not cause any additional increase in Hb difference. In conclusion, haematological and additional hemodynamical analysis show that deep-hidden anastomoses are likely to occur without any clinical consequences.
authors.affiliation: Laser Center, Academic Medical Center, University of Amsterdam, The Netherlands. j.p.vandenwijngaard@amc.uva.nl
authors.forename: Jeroen P H M
authors.initials: JP
authors.lastname: van den Wijngaard
authors.forename: Enrico
authors.initials: E
authors.lastname: Lopriore
authors.forename: Sandra M A
authors.initials: SM
authors.lastname: van der Salm
authors.forename: Arty H P
authors.initials: AH
authors.lastname: Schaap
authors.forename: Frank P H A
authors.initials: FP
authors.lastname: Vandenbussche
authors.forename: Marco C
authors.initials: MC
authors.lastname: Deruiter
authors.forename: Martin J C
authors.initials: MJ
authors.lastname: van Gemert
mesh_terms: D005260:Female; D005330:Fetofetal Transfusion / Q000601:surgery*; D006454:Hemoglobins; D006801:Humans; D017075:Laser Coagulation; D010920:Placenta / Q000098:blood supply*; D011247:Pregnancy; D014430:Twins, Monozygotic; D016157:Vascular Fistula / Q000196:embryology / Q000601:surgery*
chemical_list: D006454:Hemoglobins