Twin-to-Twin Transfusion Syndrome Differential Diagnoses

Updated: Apr 02, 2020
  • Author: Lisa E Moore, MD, MS, FACOG, RDMS; Chief Editor: Ronald M Ramus, MD  more...
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Diagnostic Considerations

The diagnosis of twin-twin transfusion is made by ultrasound. In a known monochorionic-diamniotic pregnancy, the finding of polyhydramnios of one twin with a single deepest pocket >8 cm and oligohydramnios in the co-twin with a single deepest pocket < 2 cm is diagnostic.

Growth failure may also be noted in the twin with oligohydramnios, but this finding is not part of the diagnostic criteria.

Differential Diagnoses

  • Fetal Growth Restriction

  • Premature Rupture of Membranes

  • Rupture of the amniotic sac of one twin

    Rupture of the amniotic sac of one twin can present a picture of oligohydramnios or even "stuck twin" appearance. A careful history is important to rule out an event that might have been an unrecognized rupture of the membranes. If questions remain, testing for membrane rupture should be performed.

  • Selective fetal growth restriction

    Selective fetal growth restriction occurs in monochorionic pregnancies in which unequal division of the placenta between the twins results in suboptimal growth in the twin with the lesser share of the placenta. About 10% of monochorionic pregnancies are affected. The growth-restricted twin may develop abnormalities on Doppler studies.