Final answer:
The correct answer is 'The placenta provides oxygen to the baby and excretes carbon dioxide into your bloodstream.' This occurs through the maternal-fetal blood circulation within the placenta, not through fetal breathing in the uterus.
Step-by-step explanation:
The correct response by the nurse to the query about how a baby gets air inside the uterus during a first child's initial prenatal examination is option c: 'The placenta provides oxygen to the baby and excretes carbon dioxide into your bloodstream.' While in the uterus, the fetus does not breathe air. Instead, the placenta fulfills the role of gas exchange, supplying the fetus with oxygenated blood and removing carbon dioxide. This oxygen-rich blood is delivered to the fetus via the umbilical vein, not the umbilical artery as stated in option d, and the blood delivered is not to the baby's abdomen but to the fetal circulation system, which includes the fetal heart.
In the womb, the partially collapsed lungs of the fetus contain amniotic fluid, which means they do not perform the task of breathing. It is after birth, when the umbilical cord is cut and the baby can no longer dispose of carbon dioxide through the placenta, that high levels of carbon dioxide in the newborn's blood trigger the first breaths. These first breaths see the lungs take over the oxygen-carbon dioxide exchange from the placenta. The lungs expand and fill with air, not previously present in the fetal breathing system, and the transition from placental to pulmonary respiration begins.