Trisomy 16 in mice is considered to be an animal model for Down's syndrome in human. We studied the morphologic characteristics of the heart and the edema, and their significance to the teratogenesis in this animal model.

A total of 30 dams were sacrificed to bear 125 (61.9%) normal fetuses 35 (17.3%) abnormal fetuses and 42 (20.8%) resorptions. Cytogenetic study and morphological examination were performed using microdissection agar-mount sectioning histologic examination and scanning electron microscope.

The crown-rump length was significantly shorter in abnormal (trisomic fetuses) than the normal (eusomic) fetuses. Trisomic fetuses showed massive edema at the back from the vertex to the lumbar area. Four-chamber view section of the agar-mount and histologic section showed a common atrioventricular valve bridging the left and the right atrioventricular junction. Scanning electron microscopic examination on atrioventricular valves showed three types of atrioventricular valves:five cases with common atrioventricular orifice, three cases with partitioned atrioventricular orifice and two cases with atresia of the right atrioventricular orifice.

This study confirmed the presence of massive edema and cardiac anomalies in the mouse with trisomy 16. But there was morphologic diversity of cardiac anomaly in this model.