There is a particular reflex that babies have called the Moro reflex. If you lay a baby on their back they will throw their hands out to the side, draw them in, and start crying. The reflex usually goes away at around five months of age. An article on Fatherly talks about the reflex and why it’s important for health.
It is thought to be a response against abandonment so parents don’t forget them. Even babies with very damaged brains will still have this reflex. Doctors love to test for it as a sign of a healthy brain. If a baby doesn’t do the reflex or only does it on one side, that’s a problem.
A lack of the Moro reflex can be a sign of an injury to the brachial plexus or a sign of infant brain damage, hemorrhage, birth asphyxia, and cerebral palsy. It is also a problem if the reflex lasts past six months of age. That can be a sign of drug withdrawal from maternal drug use during pregnancy.
If your baby has it too often, you can try swaddling your child. It helps babies feel they’re held right and helps them stay asleep. However, be sure to follow correct swaddling practices. If you’re uncomfortable with swaddling, lay your baby’s head down extra gently when you put them to sleep.