What is a key feature of respiratory distress syndrome (RDS) in newborns?

A key feature of respiratory distress syndrome (RDS) in newborns is the lack of surfactant. Surfactant is a substance that reduces surface tension in the alveoli (the tiny air sacs in the lungs) and is crucial for keeping them open, thus facilitating gas exchange. In premature infants, the lungs often do not produce enough surfactant, which leads to difficulty in breathing and poor oxygenation, characteristic of RDS.

Without adequate surfactant, alveoli can collapse, making it hard for the infant to breathe and impairing the ability to absorb oxygen effectively. This condition is most commonly seen in preterm infants, as surfactant production typically begins at around 24 to 28 weeks of gestation and increases as the pregnancy progresses.

The presence of surfactant, which would prevent the alveoli from collapsing, is not associated with RDS but rather with healthy lung function in infants. The other options, such as insufficient blood flow to the lungs and lack of oxygen in the blood, are related to respiratory problems but are not the defining feature of RDS itself, which is directly linked to insufficient levels of surfactant.