Final answer:
Amniocentesis is the fetal well-being test that determines fetal lung maturity. It involves the analysis of amniotic fluid for genetic health and the presence of fetal cells. Amniotic fluid is also a source of non-embryonic stem cells.
Step-by-step explanation:
The fetal well-being test that determines fetal lung maturity is called amniocentesis. During this procedure, amniotic fluid is drawn out of the mother's abdomen and analyzed for various aspects of the baby's genetic health, as well as the presence of fetal cells that can be examined for genetic defects. Amniotic fluid has also been found to be a good source of non-embryonic stem cells with the potential to differentiate into different cell types.