Final answer:
At 24 weeks, a fetus has a chance to survive if born prematurely, but after 28 weeks, the survival chances are much greater; despite this, they will still require medical assistance. By week 37, the organ systems are developed enough for the fetus to survive outside the uterus with lower risks.
Step-by-step explanation:
The age at which the internal organs have developed sufficiently to potentially allow a baby to survive outside the womb, if born prematurely, is known as the age of viability. The internal organs, such as the lungs, heart, stomach, and intestines, are formed enough by 24 weeks to give a prematurely born fetus a chance of survival. However, by the 28th week, the likelihood of survival increases significantly, and the fetus resembles a baby more closely, with the presence of eyelashes, eyebrows, and growing hair on the head.
A key period is after 26 weeks of gestation, as more than 90 percent of babies who are born after this and receive essential medical care survive. It is at 28 weeks when survival rates are much higher, yet the babies will still need help breathing due to the immaturity of their lungs. Full development of the organ systems happens by week 37, reducing the risks associated with premature birth.