What causes a newborn's mouth to appear crooked when crying?

When a newborn cries, crookedness of the mouth may be caused by facial muscle spasms, damage to the central nervous system, or facial nerve injury.

1. Facial Muscle Spasms

Newborns have delicate skin and highly sensitive subcutaneous nerves. In cold weather or low temperatures, if they are taken outdoors without adequate warmth and are exposed to cold wind or cold air, their facial muscles may spasm. This can result in a crooked mouth when the newborn cries.

2. Central Nervous System Damage

During delivery, prolonged labor with extended compression in the birth canal, or conditions such as bacterial or viral infections, hypoxia-ischemia, or physical trauma causing brain injury, may lead to damage of the central nervous system. In such cases, the newborn may also exhibit a crooked mouth when crying.

3. Facial Nerve Injury

During vaginal delivery, if the newborn's face is compressed for a prolonged period in the birth canal, the facial nerve may become injured, leading to facial nerve paralysis. Under these circumstances, the newborn typically shows mouth asymmetry or crookedness when crying.