Final answer:
Before birth, pulmonary resistance in the fetal lungs is high due to them being filled with fluid and not used for gas exchange. The resistance decreases at birth when the lungs inflate with air. Premature babies might struggle to inflate their lungs properly due to insufficient pulmonary surfactant. The option (C) is correct.
Step-by-step explanation:
Before birth, pulmonary resistance is high in the fetal lungs. This is due to the lungs being filled with fluid and not yet inflated with air, which creates a high resistance to blood flow through the pulmonary circulation. When a baby is born, this resistance decreases dramatically as the lungs inflate with air during the first breath and the fluid is cleared, allowing proper blood flow and the exchange of oxygen and carbon dioxide. During fetal development, the lungs are not used for gas exchange, and as such, the blood bypasses them through shunts like the ductus arteriosus which is part of the adaptation to the intrauterine environment.
If a baby is born prematurely before type II cells produce sufficient pulmonary surfactant, breathing difficulties can occur due to the lungs being stiff and less pliable, making them hard to inflate. Surfactant helps to reduce surface tension in the alveoli, making the lungs easier to inflate and improving pulmonary compliance. In the event of insufficient surfactant, medical intervention may be required to facilitate proper lung function and gas exchange in the newborn. Therefore, option (C) is correct.