You may have noticed your baby startling or reacting suddenly when you're trying to put them down to sleep. This is the Moro reflex, one of several normal reflexes that healthy babies are born with. It’s also one of the things that your baby’s doctor checks for right after birth and during child health visits.
What Does It Mean?
Reflexes are involuntary actions that your body automatically does without you needing to think about it. There are many types of reflexes and we are born with most of them. Newborn babies are born with several important reflexes, called primitive reflexes. These are essential for their development. Some are responses to actions while others are spontaneous movements.
When your baby’s head position suddenly shifts or if their head falls backward, they will throw out their arms away from their body and extend their neck. They also open their fingers. They will then quickly bring their arms back together, elbows bent, then relax their arms. Their fingers may also curl. Your baby may have a startled look on their face and may also cry. This reaction also happens when your baby is startled by a sudden movement, bright light, or loud sound.
This is the Moro reflex. It was first described by Ernst Moro in 1918. It can be seen as early as 25 weeks after conception and is present by 30 weeks after conception.
It disappears around two to six months of age when your baby can support their head. As your baby’s brain matures and they gain better control over their movements, these reflexes are no longer needed.
Other common reflexes in newborns include:
The rooting reflex. When you touch or stroke your newborn’s cheek or a corner of their lip, they automatically turn their head towards that side and open their mouth. This reflex of following in the direction helps them to find the nipple for breastfeeding.
The sucking reflex. When something is placed in your baby’s mouth and it touches the roof of their mouth, they will start sucking. This reflex isn’t fully developed until about 36 weeks.
How Is the Moro Reflex Tested?
Your healthcare professional will perform several tests to check on your baby’s development as part of their regular checkups. Reflexes are checked to ensure that the nervous system and the brain are developing well.
One of these tests is a Moro reflex test. Your baby will be placed lying face up on a soft, padded surface or held in the doctor’s arms. The doctor will lift your baby’s head slightly above their body and let it gently fall into the doctor’s hand. This will make your baby feel like they're falling and their arms will extend and then draw back in rapidly as part of the Moro reflex.
Some doctors may pull up gently on your baby’s arms and let them go. This also creates the feeling of falling and triggers the Moro reflex.
What to Do When Your Baby Has the Moro Reflex
Parents may be concerned when they see the Moro reflex happen for the first time. This is a normal reflex in babies. Nothing needs to be done when your baby startles. Some babies may even stop crying on their own. Other babies may need to be soothed and comforted, such as by holding them or talking softly to them.
The Moro reflex can be triggered when you’re trying to put your baby to sleep. For example, when you lean over to lay your soundly sleeping baby down in their crib, they startle awake because of the sensation of falling. At other times, they may be sleeping soundly and startle awake, sometimes even by their own movements.
Try these tips if your baby's reflexes are stopping them from sleeping soundly:
Lower horizontally. Try lowering your baby into their crib horizontally, so that you don’t tilt their head backward.
Hold your baby close. Keep your baby as close as possible to your body as you lower them. Release them only when their body is touching their mattress.
Swaddling. To help your baby sleep better, you can try swaddling. Wrapping your baby in a swaddling cloth secures their arms so that they won’t startle and fling their arms away from their body. This can calm your baby and help them to sleep better. Make sure your baby is placed on their back to reduce the risk of Sudden Infant Death Syndrome, or SIDS.
When to Call Your Doctor
Don’t worry if your baby doesn’t startle every time there’s a loud noise or bright light. But if a baby doesn’t have any Moro reflex at all, it could be because of a medical problem. These include a birth injury, problems with the brain, or general muscular weakness.
A Moro reflex that happens only on one side of the body (asymmetrical) may be because of an injury, such as damage to a nerve or spinal cord, or a fracture to the collarbone.