Final answer:
The test for fetal lung maturity is based on the lecithin to sphingomyelin ratio in the amniotic fluid, with a ratio of about 2.5 indicating mature fetal lungs. Fetal lung development continues until term, with significant maturation after the eighth month of pregnancy. Treatment for lung immaturity may include steroids and administration of surfactants.
Step-by-step explanation:
The qualitative/functional test for fetal lung maturity is based on the lecithin to sphingomyelin ratio (L/S ratio) in the amniotic fluid. A mature fetal lung typically has an L/S ratio of approximately 2.5. The L/S ratio is indicative of the presence of adequate pulmonary surfactant which is crucial for the lungs to function properly after birth. When the ratio falls between 2.4 to 1.6, there is a low risk for infant respiratory distress syndrome (IRDS), whereas a ratio of less than 1.5 signifies a high risk.
Fetal lung development is a progressive process where surfactant levels become sufficient to provide effective lung compliance typically by around the eighth month of pregnancy. Although alveolar precursors mature by about week 28 of gestation, allowing for the viability of a prematurely born baby, the full development of functional alveoli continues into childhood.
For situations where there is a concern about lung maturity and the risk of IRDS, treatments can include the administration of steroids to the mother or infant to accelerate lung development, the use of surfactants, and ventilation support to facilitate breathing.