Dicephalic parapagus twins complete hearts are present as well, which improves their chances of survival. The total number of arms may be two, three or four. Their prospects are best if no attempt is made to separate them, except in cases where one twin is clearly dying. Dicephalus means two-headed. Parapagus means joined side by side. Dicephalic twins are called: Conjoined twins appear in one in 50,000 to one in 100,000 births. Dicephalic twins represent about 11 percent of all conjoined twins. As late as the 1960s, some medical publications argued that newborn dicephalic twins should not be actively treated or resuscitated. An
Monoamniotic twins Monoamniotic twins Monoamniotic twins are identical twins that share the same amniotic sac within their mother’s uterus. Monoamniotic twins are always identical, always monochorionic and are usually termed Monoamniotic-Monochorionic ("MoMo" or "Mono Mono") twins. They also share the placenta, but have two separate umbilical cords. Monoamniotic twins develop when an embryo does not split until after formation of the amniotic sac, at about 9-13 days after fertilization. Monoamniotic triplets or other monoamniotic multiples are possible, but extremely rare. Other obscure possibilities include multiples sets where monoamniotic twins are part of a larger gestation such as triplets, quadruplets, or more. Monoamniotic