Underoxygenation

Because uterine contractions tend to compress the baby and restrict blood flow in some areas of the body during birthing, transient underoxygenation of brain (hypoxia) commonly occurs during birth.

Underoxygenation is a bigger concern than slight overoxygenation. The yeast will very quickly remove all of the oxygen from the wort when pitched.

In imperfect or shallow breathing, only a portion of the lung cells are brought into play, and a great portion of the lung capacity is lost, the system suffering in proportion to the amount of underoxygenation.