Re A (conjoined twins) indicated that Gracie was the stronger sibling who was sustaining the life of Rosie. Rosie had only survived birth due to a shared common artery that enabled her sister Gracie to oxygenate blood for both twins. If surgically separated, Gracie had a 94% survival rate, but Rosie was guaranteed to die. However, if they were left conjoined, then Gracie's health—which was already rapidly deteriorating—was predicted to fail before they were six months old. Gracie's death would inevitably result in Rosie's. At first instance, Mr Justice Johnson was left to decide the case without any direct precedents to guide him but
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