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The importance of determining chorionicity in twin gestations

A 32-year-old G2P1001 was diagnosed with twins at her initial ultrasound (U/S) examination in her obstetrician’s office at 12 weeks’ gestation. At her next U/S examination, scheduled at 20 weeks to evaluate fetal anatomy, a dividing membrane was not visualized between the twins, and a monoamniotic gestation was suspected. Maternal-fetal medicine consultation was requested, and a monochorionic-diamniotic gestation was subsequently diagnosed—complicated by severe twin-twin transfusion syndrome (TTTS). 

Last Reaffirmed: Feb 1, 2013