The Moro reflex is a term commonly associated with newborns. It is a primitive, innate reflex that is present even during prenatal development. This reflex typically disappears between 4 to 6 months of age. The intensity of the Moro reflex varies from child to child.
It is one of the most common causes of waking and short sleep in newborns.
How the Moro Reflex Manifests
If you have a newborn at home, you might notice moments when your baby, lying on their back, suddenly jerks their arms out. The fingers spread apart, and there is a slight extension of the neck and spine. The baby then retracts the arms, often followed by a loud cry.
This reflex can occur when the baby feels like they are falling, such as when being lifted. However, the baby doesn’t need to actually be falling; the reflex is a response to a sudden stimulus. This can be auditory (a loud unexpected noise), visual (bright light), or tactile (touch). The baby also reacts similarly to a loss of balance.
The Moro reflex is instinctive, as if the baby is trying to grasp onto the mother’s body. In reality, it represents a protective motor reaction to a sudden disturbance of bodily equilibrium or extreme sudden stimulation (1) . In premature babies, the reflex is less intense than in full-term newborns (2).
Moro Reflex and Sleep
The Moro reflex is often the reason why newborns wake up 10-15 minutes after falling asleep. They wake up due to the jerking motion of their arms. As mentioned earlier, babies develop this reflex during prenatal development. Even in the womb, the baby involuntarily “throws” their arms out. However, in the womb, the baby does not have as much space, and the uterus restricts the arm movements. After birth, the baby suddenly has more space, which is why they wake up from the jerking motion during sleep.
If the baby sleeps in a carrier, wrap, or swaddle, their sleep can be calmer and longer, as they are less likely to wake up due to the Moro reflex. Nowadays, there are many swaddles, wraps, and sleep sacks available on the market specifically designed for newborns. You can also swaddle your baby with a cloth diaper. To make swaddling effective, you must choose the right swaddle for your baby, ensure the swaddle is snug, and make sure the fabric does not press on the baby anywhere. Even though it may seem repetitive, safety is paramount when it comes to sleep, so follow the safe sleep guidelines when swaddling.
Source
(1) Zafeiriou DI. Primitive reflexes and postural reactions in the neurodevelopmental examination. Pediatr Neurol. 2004 Jul;31(1):1-8. doi: 10.1016/j.pediatrneurol.2004.01.012. PMID: 15246484.
(2) hSohn M, Ahn Y, Lee S. Assessment of Primitive Reflexes in High-risk Newborns. J Clin Med Res. 2011 Dec;3(6):285-90. doi: 10.4021/jocmr706w. Epub 2011 Nov 10. PMID: 22393339; PMCID: PMC3279472.