The drainage of mucus from one or both nostrils in choanal atresia can cause:

In cases of choanal atresia, which is an obstruction of the nasal passages, drainage of mucus from one or both nostrils can lead to cyanosis when feeding. This is primarily due to the fact that infants are obligate nasal breathers, meaning they rely on their noses for breathing, especially during feeding when they may not be able to breathe through their mouths.

When the nasal passages are obstructed, the infant has difficulty getting enough air, leading to episodes of hypoxia, particularly while sucking and swallowing. This can manifest as a bluish discoloration of the skin (cyanosis), signaling that the baby is not receiving adequate oxygen, especially during feeding when the demand for oxygen increased.

The other options, while they may have some relevance in a broader context of respiratory distress or other medical issues, do not directly relate to the specific physiological response that occurs due to the obstruction caused by choanal atresia during feeding.