Does a fetus breathe when it's inside a womb?

A fetus does not truly "breathe" in the womb in the same way that a person outside the womb does. Here are some key points to clarify this:

Oxygen Supply

The fetus receives its oxygen and has its carbon dioxide removed through the placenta and the umbilical cord, not through breathing air. The placenta acts as the primary organ for gas exchange, providing the fetus with the necessary oxygen and nutrients345.

Fetal Breathing Movements

Although the fetus does not breathe air, it does exhibit breathing-like movements. These movements, which can be observed from around 20-21 weeks of gestation, involve the contraction and relaxation of the diaphragm and other respiratory muscles. This practice helps the fetus prepare for breathing after birth and may also aid in the development and maturation of the lungs245.

Amniotic Fluid

The lungs of the fetus are filled with amniotic fluid, not air. These breathing movements involve the inhalation and exhalation of this fluid, which helps in the production of pulmonary surfactant and the maturation of the alveoli234.

In summary, while a fetus does not breathe air in the womb, it does engage in breathing-like movements that are crucial for the development and preparation of its respiratory system for life outside the womb.