How does mechanical compression during vaginal delivery affect the lungs?

• A. It increases pressure in the alveoli
• B. It creates a positive pressure to expel fluid
• C. It creates negative pressure, allowing air intake
• D. It decreases lung expansion

Answer: (C)

During vaginal delivery, mechanical compression of the fetus during passage through the birth canal exerts external pressure on the thoracic cavity. This pressure can help facilitate the expulsion of amniotic fluid from the lungs, which is crucial for effective lung function after birth.

As the chest is compressed during delivery, when the baby is born and the external pressure is released, the negative pressure created allows for the first inhalation. This negative pressure draws air into the lungs, initiating respiration. The process enhances the transition from fetal to neonatal life, as it encourages lung expansion by ensuring that air enters the previously fluid-filled lungs.

The correct answer captures this physiological mechanism, highlighting how the change in pressure contributes to the lung's ability to expand and function in the newborn. Other options either misrepresent the nature of pressure changes during delivery or do not accurately describe the result of mechanical compression on lung function.