Which condition is indicated by a low L/S ratio?

A low lecithin-to-sphingomyelin (L/S) ratio serves as an important indicator of fetal lung maturity. Lecithin and sphingomyelin are phospholipids found in surfactant, with lecithin providing the necessary properties for lung function and surface tension reduction in the alveoli. A low ratio indicates that the amount of surfactant (lecithin) is insufficient relative to the amount of sphingomyelin, signaling underdeveloped lungs.

When the L/S ratio is low, it correlates with an increased incidence of hyaline membrane disease (HMD), also known as neonatal respiratory distress syndrome (NRDS), particularly in preterm infants. This condition arises due to inadequate surfactant production, leading to increased surface tension in the alveoli, causing atelectasis (collapse of the lung) and impaired gas exchange. Infants with HMD often require respiratory support and surfactant replacement therapy.

The other options do not align with the implications of a low L/S ratio. Healthy lung maturity would be associated with a higher L/S ratio, reflecting adequate surfactant levels. Normal respiratory function would not be expected in the context of a low L/S ratio, and a higher survival rate