What is the effect of pregnancy on the diaphragm?

• A. The diaphragm moves downward during inspiration
• B. The diaphragm is lifted by the uterus
• C. The diaphragm moves laterally
• D. The diaphragm is pushed up by the uterus

Answer: (D)

During pregnancy, the enlarging uterus rises into the abdominal cavity and pushes the diaphragm upward into the thoracic cavity. This elevation raises the diaphragm’s resting position and reduces how far it can descend with each breath, so the vertical dimension of the chest is decreased. As a result, inspiratory capacity and functional residual capacity are reduced, while tidal volume increases to meet higher oxygen needs, leading to a higher overall ventilation. The diaphragm being pushed up by the uterus is the main mechanical effect to remember, even though the diaphragm still moves with each inspiration.