Thoracoomphalopagus diagnosed before delivery.

Twins may be dizygotic or monozygotic. Of the monozygotic twins, 25% to 30% are dichorionic and 70% to 75% are monochorionic. Whilst all the dichorionic twins are diamniotic, very occasionally some monochlorionic ones may be monoamniotic; some of these may be conjoined. A case of conjoined twins was diagnosed during pregnancy. The two girls were delivered by elective classical caesarean section. They were joined together from just above the xiphisternum to the umbilicus and were successfully separated. Recent literature is reviewed.