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Lung Development in Newborns

By Regan Hennessy ; Updated June 13, 2017

Although your baby’s lower respiratory system started forming shortly after its heart began to beat, the lungs are among the last organs to fully mature before birth. Most newborns come into the world ready to breathe on their own, but some don’t, particularly those who are born prematurely. These newborns, equipped with underdeveloped lungs, are much more likely to suffer respiratory problems.


The lungs make their first appearance in the form of tiny buds at 26 days gestation. During the first and second trimesters, the bronchial tree and major airways form. Prior to birth, the lungs form tiny air sacs, called alveoli; they produce a lubricating fluid called surfactant that keeps the lungs moist and enhances gas exchange. The surfactant system matures and continues to develop until birth. Babies don’t use their lungs before birth because they receive oxygen through the umbilical cord.


As soon as a baby is born, he should be able to inhale oxygen on his own. As uterine contractions push the baby through the birth canal, the constriction of the body helps press excess amniotic fluid from the baby’s lungs. Once delivered, the baby inhales rapidly, often in the form of a gasp or cry that usually occurs within 10 seconds of birth. This first inhalation causes the lungs to inflate, which allows them to start operating properly -- bringing oxygen into the body and sending carbon dioxide out. Following birth, the lungs continue to mature as they develop a more extensive network of alveoli.

Premature Newborns

Babies born before their lungs have developed adequately may succumb to respiratory distress syndrome (RDS). This condition is most common in premature newborns, particularly those born before 28 weeks' gestation. Inadequate surfactant production allows the air sacs to stick together and collapse, which causes breathing problems. Signs of RDS typically appear within a few moments of birth and may include pauses in breathing, the appearance of bluish skin, rapid breathing and physical signs of breathing difficulty such as grunting and flaring of the nostrils. Infants suffering from RDS require immediate supplemental oxygen that may be necessary for weeks until the lungs have matured enough for them to breathe properly on their own.


Newborns born prematurely are more likely to suffer respiratory problems arising from immature lungs, so preventing premature birth is extremely important. If you experience signs of premature labor, your doctor may recommend an amniocentesis; this procedure helps determine how mature your unborn baby’s lungs are by checking the amniotic fluid for the presence of lung surfactant. In certain instances, your doctor may opt to administer certain medications, such as corticosteroids, which help boost prenatal lung development and may minimize postnatal respiratory problems.

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