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What Is Moro (Startle) Reflex In Babies And When Does It Go Away? 

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Most responses of newborns and infants are reflexive in nature. For instance, if you stroke their cheek, they turn their head, or when you put a finger in their mouth, they start sucking it. These are called primitive reflexes.

A reflex is an involuntary reaction or movement. Various reflexes or automatic responses, including rooting reflex, suck reflex, stepping reflex, grasp reflex, tonic neck reflex, and Moro (startle) reflex, occur at different stages of a baby’s development (1).

In this post, we tell you about Moro or startle reflex, what it looks like, what triggers it, and more.

What Is A Moro Reflex In Infants?

Moro or startle reflex is a type of involuntary response seen in newborns. It usually occurs when a baby is startled by a loud noise or movement (2). The reflex was first described by Dr. Ernst Moro, an Austrian physician, and since then, it is also called the Moro reflex (3).

What Does Moro Reflex Look Like In Babies?

A stimulus could startle the baby and trigger the Moro reflex, which causes the baby to throw their head back and extend out their arms and legs. The baby’s arms extend sideways, while the palms face upwards with the thumbs flexed. The baby may also cry a little.

When the reflex ends, the baby pulls back their legs and arms with flexed elbows. The infant calms down and relaxes (1) (4).

What Triggers The Moro Reflex?

The following stimuli could trigger the Moro or startle reflex (1) (2).

  • Loud, abrupt sound
  • Baby’s own cry
  • Sudden movement
  • Sensation of falling (when being picked up or laid down)

When Does Moro Reflex Start?

Moro reflex is present in newborns and peaks during the first month. Different babies show startle reflex in varying degrees of intensity (2).

Is Moro Reflex An Issue In Newborns?

It is a normal reflex among newborns. If startle reflex is absent in newborns, it is a sign of concern. Doctors usually check for this response right after the baby’s birth and during subsequent visits. The absence of a startle reflex in newborns may be suggestive of the following (4).

  • If absent in limbs on both sides of the body, it may indicate damage to the spinal cord or brain.
  • If absent in limbs on one side of the body, it may indicate injury to the nerves that go from the lower neck and upper shoulder into the arms or a broken shoulder bone. It may also indicate other injuries, such as injuries to the nerves that go to the legs or fractures.

How Long Does Moro Reflex Last In Babies?

Moro reflex lasts up to two months of age (2). In some instances, it may last up to three months and disappear completely by six months (5).

It is important to note that the presence of startle reflex in older babies and children is considered abnormal.

When To Call A Doctor?

If the Moro reflex is absent or abnormal in babies, then it may require further investigation. The doctor will perform a physical examination and discuss the medical history, including family medical history, labor and birth details, and other anomalies in the baby.

Further tests may be conducted to assess the baby’s muscles and nerves. These diagnostic tests may include shoulder X-rays or tests for brachial plexus injury (4).

You may also consult a doctor if the Moro reflex persists beyond six months. In such cases, the doctor could conduct tests to assess the baby’s normal growth and check for any regression in developmental milestones.

How To Reduce Moro Reflex In Infants?

An intense Moro reflex may sometimes interfere with the baby’s sleep. You may try the following to comfort your baby.

  • Swaddling: The technique of wrapping a baby from the neck down in a light and breathable cloth is called swaddling. It offers comfort and warmth and prevents frequent awakenings that may occur due to the baby’s reflexes.
  • Baby wearing: Baby wearing involves carrying a baby in a carrier that ensures skin-to-skin contact. Many believe that baby wearing calms the baby down, reduces crying, and builds connection.
  • Room-sharing: The American Academy of Pediatrics recommends placing your baby’s cribs in the same room as yours (6). It may help make it easier for you to soothe the baby and control any disturbances, such as loud sounds, that may lead to the Moro reflex. Remember not to place the baby in the same bed as yours since bed-sharing may increase the risk of sudden infant death syndrome (SIDS).
  • Correct transferring methods: Abrupt movements are one of the reasons for startle reflex. Therefore, when transferring or shifting your baby, take extra care to avoid such movements. Be gentle and handle the baby carefully when placing them in their crib once they have fallen asleep. Place the head of the baby once their back is in contact with the mattress. This technique could help avoid the sensation of falling and prevent triggering the Moro reflex.
  • Offering a pacifier: Once the baby is four weeks old, you may offer them a pacifier during naps and bedtime (7). The sucking action could calm babies and may make them less prone to startling while asleep. Do not force the baby to use a pacifier, and do not tie it to the baby’s clothes or crib.

Ages And Stages Of Moro Reflex

  • Birth to 1 month: Moro reflex is present at birth and peaks during the first month. The reflexes are frequent and prominent during this phase since the baby is new to the various external stimuli. Swaddling in such cases could soothe the baby.
  • 2 to 3 months: At this stage, the baby is more familiar with your touch and presence. Hence, they will be calmer and sleep longer. However, if they get startled and wake up, make sure to gently calm them down with your touch and help them go back to sleep.
  • 4 to 6 months: By this time, the babies have more control over their muscles and movements. The startle reflex begins to improve, and it is quite likely your baby may not have it beyond the age of two months. Nevertheless, the reflex gradually disappears by the age of six months old.

Other Types Of Newborn Reflexes

Let us discuss other types of reflexes seen in babies (1) (8).

  • Rooting reflex: Rooting reflex occurs when you touch a baby’s mouth (near the corners). The baby will turn their head or open their mouth to root in the direction of the touch. This reflex helps the baby find the bottle or breast for feeding. It usually disappears by the time the baby is four months old.
  • Grasp reflex: When you touch the baby’s palm with a finger or object, they try to grasp the finger or the object. The grasp reflex of the hands disappears by the age of five to six months old, while the reflex of the toes stays up to nine to 12 months.
  • Tonic neck reflex: When the baby’s head turns towards a direction, the arm on that side stretches out, while the arm on the opposite side bends at the elbow. It is also known as the fencing reflex and lasts till the baby is five to seven months old.
  • Stepping reflex: The baby tries to take steps or dance when held upright or when made to stand on a surface with support. It is also known as dancing or walking reflex, and it disappears by the time a baby is two months old.
  • Suck reflex: Babies start to suck when the roof of their mouth is touched. This reflex is not fully developed until 36 weeks of gestation. Therefore, in premature babies, this reflex is often weak or immature. The suck reflex usually lasts up to four to six months, which is the age when most babies are ready for solid food.

Moro reflex is seen in newborns and disappears by the time they are two months old. The absence of startle reflex in one or both sides may indicate an injury or damage to the brain or spinal cord. If you notice the lack of or abnormal startle reflex, consult a doctor for further examination.

References:

MomJunction's health articles are written after analyzing various scientific reports and assertions from expert authors and institutions. Our references (citations) consist of resources established by authorities in their respective fields. You can learn more about the authenticity of the information we present in our editorial policy.
1. Newborn Reflexes; Stanford’s Children Health
2. Newborn Reflexes; Healthy Children; American Academy of Pediatrics
3. Dick Hoefnagel and Dieter Luders, Ernst Moro; American Academy of Pediatrics
4. Moro reflex; U.S. National Library of Medicine
5. Christopher W. Edwards and Yasir Al Khalili, Moro Reflex; StatsPeral publishing; NCBI
6. Rachel Y. Moon, How to Keep Your Sleeping Baby Safe; Healthy Children; American Academy of Pediatrics
7. Pacifiers: Satisfying Your Baby’s Needs; Healthy Children; American Academy of Pediatrics
8. Development of Infant Feeding Skills; USDA