An Unguarded Tricuspid Valve Orifice Diagnosed by Autopsy.

Fetal unguarded tricuspid valve orifice (UTVO) is characterized by a complete or partial absence of the tricuspid valvular tissue or sub-valvular apparatus and only case reports are available at present. We report a UTVO diagnosed by fetal autopsy. An 18-week fetus was diagnosed by prenatal ultrasound with tricuspid dysplasia with 'to-and-fro' flow across the right-sided heart. Fetal autopsy showed partial agenesis of tricuspid valve instead of valvular dysplasia. This supported a diagnosis of UTVO. Fetal autopsy can differentiate UTVO form other valve abnormalities. The 'to-and-fro' flow pattern across the right atrioventricular orifice could be used to differentiate UTVO from other valve dysplasias on echocardiography.