Conjoined twins dead twin from the surviving twin. The result was partly successful as the remaining twin lived for three days after separation. The next case of separating conjoined twins was recorded in 1689 in Germany several centuries later. The first recorded successful separation of conjoined twins was performed in 1689 by Johannes Fatio. In 1955, neurosurgeon Harold Voris (1902-1980) and his team at Mercy Hospital in Chicago performed the first successful operation to separate craniopagus twins (conjoined at the head), which resulted in long-term survival for both. The larger girl was reported in 1963 as developing normally, but the smaller was
Monochorionic twins Monochorionic twins Monochorionic twins are monozygotic (identical) twins that share the same placenta. If the placenta is shared by more than two twins (see multiple birth), these are monochorionic multiples. Monochorionic twins occur in 0.3% of all pregnancies. 75% of monozygotic twin pregnancies are monochorionic; the remaining 25% are "dichorionic diamniotic". If the placenta divides, this takes place after the third day after fertilization. Monochorionic twins generally have two amniotic sacs (called Monochorionic-Diamniotic "MoDi"), but sometimes, in the case of monoamniotic twins (Monochorionic-Monoamniotic "MoMo"), they also share the same amniotic sac. Monoamniotic twins occur when the split takes place after