Neonatal respiratory distress syndrome (RDS) is a breathing problem that develops in babies born prematurely. RDS can also be caused by factors other than premature birth. These include infections and insufficient oxygen in the blood.

What is going on in the body?

The lungs start developing when a baby has been in the womb for about one month. It takes time for the lungs to develop completely. When babies have been in the womb for 26 to 28 weeks, their lungs have the structure needed for breathing. However, they are still missing a vital component. This is a substance called surfactant.

Surfactant is a chemical produced by certain lung cells. It acts like a lubricant for the smallest part of the airways, called the alveoli. Each time a person exhales, the alveoli collapse. They open again when the person breathes in. The surfactant allows the alveoli to open easily. Otherwise, a large amount of friction would be created with each breath.

RDS occurs when there is not enough surfactant in the lungs. This causes the alveoli to collapse and makes it difficult for them to open again. The collapse of the alveoli is called atelectasis. Premature babies have a hard time building up enough air pressure to open the collapsed alveoli. This makes it difficult for them to breathe.

Surfactant does not usually start being made until a baby has been in the womb for 32 to 34 weeks. The majority of babies born before 28 weeks of pregnancy develop RDS. In general, the earlier a baby is born, the less surfactant there is in the lungs and the more trouble the baby has breathing. After the 34th week, the level of surfactant is high enough to show up in the amniotic fluid that surrounds the baby in the womb.

What are the causes and risks of the condition?

Factors that increase a baby's risk of RDS include: