How fast would it take someone to die from another organism bursting from their body?
Have you heard about something called mammalian birth?
It happens all the time. A child is not part of the mother, contrary to some folk-beliefs. The child gets half its DNA from the father and half from its mother. It is not an exact copy of either and has its own unique identity.
A child is an extremely efficient parasite that grows inside another creature after being implanted by a virus called "sperm". It feeds off its 'mother' and like a cuckoo gets fed and brought up by its 'parents' by a very clever strategy of manipulating their hormones so that they 'love' it.
ItsIt's survivable for the mother but there is always a risk of her death if things go wrong.