What happens to a fetus that is not deemed legally viable?

A fetus that is not deemed legally viable cannot survive outside the uterus. Legal viability usually refers to the stage of development when a fetus is capable of sustaining life independently from the mother's body, typically around 24 weeks of gestation but it can vary based on medical advancements and conditions. If a fetus is determined to be not viable, it means it has not reached this critical point in development and lacks the necessary maturity to survive without immediate medical intervention or assistance.

This definition clarifies why the other options do not apply. For example, eligibility for adoption pertains to circumstances where a child can be taken into care, which isn't relevant until after birth. Premature delivery refers to the birth of a viable fetus before the expected date, while the development of natural immunity typically occurs after birth through exposure to pathogens or maternal antibodies. Thus, when considering viability, the primary focus is on the fetus’s inability to live outside the womb.