The Development of Breathing

During life in the womb, immersed in amniotic fluid, the fetus does not breathe in the conventional sense of the term, as there is no air present. Throughout pregnancy, the fetus does not use its own lungs for respiration but receives oxygen through the placenta via the umbilical cord. When the mother inhales, her blood becomes enriched with oxygen, which is transported to the fetus through a complex network of placental blood vessels. At the same time, the fetus releases carbon dioxide, which passes into the mother’s bloodstream and is eliminated through maternal exhalation. This interconnected mechanism ensures fetal survival and well-being until birth.

Fetal Lung Development

The respiratory system develops progressively throughout pregnancy according to a precise timeline:

• Day 24: beginning of the development of the respiratory tree.
• Day 28: formation of the primary bronchi.
• Week 16: formation of the bronchioles.
• Week 28: structural completion of the lungs, including the alveoli.

Around the 32nd week of gestation, although the lungs are not yet fully mature, they allow the fetus to perform thoracic breathing movements in preparation for independent breathing. Full lung maturation, including adequate production of surfactant—a substance essential for proper lung function outside the womb—occurs around the 35th–36th week of gestation.

The fetus requires the entire duration of pregnancy (approximately nine months) to gradually complete its physiological development, thereby preparing the body for extrauterine life.

The Onset of Independent Breathing at Birth

Immediately after birth, the first breath marks the opening of the pulmonary alveoli for the gas exchange required to oxygenate the blood. Most newborns take their first breath within 20 seconds of birth and establish a regular breathing pattern within 90 seconds. During the first moments of life, newborns may experience brief respiratory pauses while their respiratory system adapts to the new extrauterine environment.

During vaginal delivery, thoracic compression followed by chest re-expansion facilitates the passive entry of air into the lungs. However, the primary stimuli triggering spontaneous breathing are skin cooling and mechanical stimulation, which activate the respiratory center in the brain.

Development of Breathing in Children

The entire process of respiratory development represents an extraordinary physiological mechanism that accompanies the child from intrauterine life to complete pulmonary maturation, enabling survival and successful adaptation to life outside the womb.