Final answer:
Choanal atresia most likely explains the condition of apnea when breastfeeding in a newborn, as it causes a blockage in the nasal passage that interferes with breathing when the mouth is occupied during feeding.
Step-by-step explanation:
The condition described where a newborn infant experiences apnea when breastfeeding but recovers quickly when breastfeeding is discontinued is most likely due to Choanal atresia. Choanal atresia is a congenital disorder where the back of the nasal passage is blocked, typically by abnormal bony or soft tissue due to failed recanalization of the nasal fossae during fetal development.
When the infant is breastfeeding, the mouth is occupied, and the blockage of the nasal passage can lead to difficulty breathing, or apnea. Once breastfeeding is stopped, the infant can breathe through the mouth, which alleviates the apnea. The other options, such as infant respiratory distress syndrome (RDS), tetralogy of Fallot, and diaphragmatic hernia, are less likely to cause intermittent apnea specifically associated with feeding.