Surfactant is a fatty substance produced by the lungs that helps to keep tiny air sacs (alveoli) open for gas exchange. Surfactant is only produced within the last few weeks of pregnancy. Unfortunately, preterm infants miss out on this part when they are delivered too early.
In utero, the baby does not breathe with his lungs since he is floating in amniotic fluid. It is during birth when the lungs finally kick in and start working. During the baby’s first breaths, the lungs are expected to take on major tasks that they have never performed before—that is, empty themselves of fluid, take a large gulp of air, absorb oxygen, and pass it into the bloodstream. In order to do this, lungs need the miraculously foamy fluid (surfactant) that forms a very thin coating inside the alveoli.
Lungs are spongy and wet, and the surfactant keeps the surfaces of the air sacs from getting too wet. Without surfactant, the air sacs can’t inflate well when the baby inhales and will collapse when the baby exhales. When the inside of the air sacs are stuck together like a deflated wet balloon, it takes a lot of work to re-inflate them. The baby must work extra hard to inhale air into the alveoli, only to have them collapse again when exhaling. Soon, breathing becomes very labored, and most preemies don’t have enough energy to maintain this struggle for very long. As a result, the baby becomes exhausted and will experience respiratory distress.
Surfactant therapy is the main reason why preemies are now able to survive when born at a very early age. The stress of labor and postpartum life actually stimulates babies’ lungs to start producing surfactant within 3-4 days after birth, at which point the baby’s breathing starts to improve. Babies who have been under stress in the womb before delivery are actually born with more mature lungs and are less likely to experience respiratory distress. If needed, however, the baby can receive several doses of artificial surfactant after delivery in order to stent open the lungs.