The "T-Sign" of Monochorionic Twins

Determining chorionicity is paramount for twin pregnancy surveillance.

A thin dividing amniotic membrane that inserts into the shared placenta at a perpendicular, characteristic "T" configuration confirms a monochorionic-diamniotic gestation.

This must be differentiated from the thick, triangular "twin-peak" or "lambda" sign characteristic of dichorionic pregnancies.

Identify the "T-sign" early to triage the patient into a high-risk ultrasound monitoring protocol for monochorionic complications like Twin-Twin Transfusion Syndrome.