Monoamniotic twin gestations, although rare, are associated with a high perinatal mortality rate. Early antenatal diagnosis is important to ensure optimal perinatal care. However, the diagnosis can be difficult to confirm, especially in late gestation when a dividing membrane may be difficult to visualize. Intra-amniotic injection of Renografin followed by a single-slice computed tomographic scan at the level of the umbilicus is described. This imaging method assisted in the confirmation of monoamniotic twinning.