Babies do not breathe air in the womb as we do after birth. Instead, they receive oxygen through the placenta and umbilical cord from their mother's bloodstream. The mother inhales oxygen, which enters her blood, and this oxygen-rich blood is transferred via the placenta and umbilical cord to the fetus. At the same time, carbon dioxide and other waste gases from the baby pass back through the umbilical cord and placenta to the mother's bloodstream to be exhaled
. While in the womb, the baby's lungs are filled with amniotic fluid and not air. The baby practices "breathing" movements by inhaling and exhaling small amounts of amniotic fluid, starting around 10 to 20 weeks of gestation. These fetal breathing movements help develop the respiratory muscles and lungs but do not involve actual gas exchange. This practice prepares the lungs and muscles for breathing air after birth
. At birth, the baby takes its first breath, which inflates the lungs and replaces the fluid with air. The process of labor and delivery helps expel much of the fluid from the lungs. Pulmonary surfactant, produced by the lungs before birth, reduces surface tension and allows the lungs to expand properly during the first breaths
. In summary:
- Oxygen is supplied to the fetus via the placenta and umbilical cord, not by lung breathing.
- The fetus practices breathing movements with amniotic fluid to prepare lungs and muscles.
- The lungs are filled with fluid in utero and only inflate with air after birth.
- The first breath after birth initiates normal lung breathing and oxygen exchange
