4. Baby dies in the womb or during child birth. Does not turn. This could be very important because even if the baby is dead, it could show that newborns might not be infected. Ironically, the death of the baby could provide hope for humanity of a world without zombies.
Unless the zombie infection agent somehow prevents the birth of live babies even if it doesn't reanimate them, in which case the current generation would have to acknowledge that they will be the last humans ever.