[Prevalence and complications of monochorionic diamniotic twin pregnancy].

Background: Monochorionic biamniotic (MC/BA) twin pregnancies are at higher risk for twin-to-twin transfusion syndrome (TTTS), selective intrauterine growth restriction (sIUGR) and structural defects.
Material and Method: During an 18 months period all MC/BA twins referred to our unit for clinical surveillance were evaluated. Chorionicity was assessed based on the characteristics of the intertwin amniotic membrane. MC complicated cases were labeled either as, TTTS or sIUGR and classified according to severity. All cases were closely evaluated for structural defects.
Results: There were 34 MC/BA pregnancies, from them 20 presented TTTS, 6 in a moderate stage of severity, and 14 severely affected. Four cases had sIUGR, all severely affected. Four pregnancies showed a structural defect, 2 cardiac, 1 urological, and 1 open neural tube defect. Six twin MC/BA pregnancies underwent gestation without complications.
Conclusion: The presence of a MC/BA twin pregnancy warrants close monitoring, including a detailed anatomical review and hemodynamic assessment of the umbilical arteries and ductus venosus of both twins.