Antepartum ultrasonographic diagnosis of ischiopagus: a rare variety of conjoined twins.

Conjoined twinning occurs only once in every 50,000 births.• The antepartum ultrasonographic diagnosis of this anomaly was first reported in 1977.2 Since that report, five similar cases have been added to the literature.:' ; Each of these re· ports concern the most common type of conjoined twin, thoracopagus or the combination thoraco·om· phalopagus. We believe that this is the first reported antepartum ultrasonographic diagnosis of ischiopagus.