If the identical twins share a placenta they're at a higher risk of having twin-to-twin transfusion syndrome. This typically leads to one twin gaining a lot of nourishment than the other, and having the next birth weight as a result.
Umbilical cord entanglement and compression if the twins share an amniotic sac. Purely thanks to the packed conditions that occur within the mother’s womb.
With identical and non-identical twins, there is an increased risk of pregnancy and birth complications. there's additionally an increased chance of prematurity and associated issues.