Newborns come with a set of automatic responses that are sometimes startling to first-time parents — a hand reflexively gripping a finger with surprising strength, arms thrown wide at a loud noise, the whole body briefly going stiff. These are primitive reflexes, and they exist for clear reasons. Knowing what they are, what they're for, and when each one should fade demystifies a lot of newborn behaviour.
Healthbooq covers newborn behaviour and the milestones across the first months.
Why Newborns Have Reflexes At All
Primitive reflexes are stereotyped motor patterns wired into the brainstem and lower brain structures (subcortical circuits). They run before the cerebral cortex has finished maturing enough to take over voluntary control of those movements. As the cortex matures and inhibits the subcortical patterns, each reflex fades on its expected timeline.
They serve a few overlapping purposes:
- Direct survival — rooting and sucking enable feeding from the first hour.
- Possible evolutionary remnant — the palmar grasp may have helped primate infants cling to a mother's fur.
- Distress signalling — the Moro brings the carer over by combining a startle, a flailing motion, and usually a cry.
- Neurological check — for clinicians, the presence and symmetry of these reflexes is an immediate assessment of the integrity of specific pathways.
The reflex assessment is part of the NIPE — the newborn examination within 72 hours of birth. Asymmetric or absent reflexes flag specific neurological concerns and prompt further investigation.
The Moro (Startle) Reflex
The most dramatic, and the one most parents notice in the first days. The trigger is anything that suggests sudden falling or loss of support: a loud noise, a jolt, the head dropping back unexpectedly, or being placed down on a flat surface a fraction too quickly.
The response unfolds in two phases:
- Spreading — arms are flung wide and slightly back, fingers spread, often with the legs extending too. Looks startling.
- Drawing in — arms come back across the chest, fingers close, often followed by a cry.
The whole sequence takes about 1 to 2 seconds.
Timeline: present from birth (and even before — it has been observed on antenatal ultrasound). Fades from around 3 months and is gone by 4 to 6 months as the cortex inhibits it.
Why it matters in real life: the Moro is the single biggest reason that swaddled newborns sleep more soundly than unswaddled ones. As babies cycle through sleep stages, the transitions between deeper and lighter sleep can trigger small Moros that wake them. Swaddling holds the arms still and stops the reflex from interrupting sleep. This is why swaddling becomes less helpful around 3–4 months — the reflex is fading anyway, and the baby is starting to roll, at which point swaddling becomes unsafe.
Flags:- Asymmetric Moro — one arm not responding, or weaker than the other — can mean Erb's palsy (brachial plexus injury during delivery), clavicle fracture, or other localised injury. Same-side weakness in arm and grip is the picture.
- Absent Moro at birth — can suggest significant central nervous system depression (severe hypoxic injury, sedating maternal medication, severe prematurity).
- Persistent Moro past 6 months — flag at the 6-month or 8-month review; can be a sign of central nervous system pathology.
Rooting Reflex
Stroke a finger gently down the cheek or at the corner of the mouth. The baby turns their head toward the stroke, opens their mouth, and starts searching with the tongue. This is the rooting reflex — the feeding-seeking program.
Timeline: present from birth. Integrates with voluntary feeding behaviour by 4 to 6 months.
Why it matters: rooting is what lets a newborn find the breast. The reflex is strongest when the baby is calm and slightly hungry; it fades when they are full or asleep. Crying overrides rooting, which is one of the reasons feeding works much better when caught at early hunger cues rather than at the crying stage.
Flags: persistent absence of rooting in the first weeks alongside poor feeding warrants assessment.
Sucking Reflex
Place a finger pad up against the roof of the baby's mouth. The baby produces rhythmic, strong sucking. The reflex coordinates suck-swallow-breathe in a tightly choreographed pattern that is one of the more impressive bits of newborn motor control.
Timeline: present from about 32 weeks gestation onwards (which is why babies born before 32 weeks usually need help with feeding). Integrates with voluntary feeding by 4 to 6 months.
Why it matters: the sucking reflex is the basis of the calming effect of dummies, fingers, and breastfeeding for non-nutritive comfort. Suck activates the parasympathetic system and lowers heart rate.
Flags: poor or uncoordinated suck in a term baby suggests neurological or oral motor issues; persistent inability to coordinate suck-swallow-breathe is investigated.
Palmar Grasp Reflex
Press a finger into the centre of the baby's palm. The fingers close tightly around it. Some babies can grip strongly enough to briefly bear their own weight (do not test this — they cannot voluntarily release if they slip).
Timeline: present from birth. Fades by 4 to 6 months as voluntary reaching and grasping develop.
A useful detail: while the palmar grasp is dominant, voluntary release is not yet possible. This is why young babies cannot deliberately let go of an object — they will pass it from hand to hand, but cannot drop it on cue. Voluntary release develops around 6 to 9 months.
Flags: asymmetric grasp on the same side as an asymmetric Moro suggests Erb's palsy or brachial plexus injury. A persistent palmar grasp past 6 months interferes with voluntary fine motor development.
The Plantar Grasp
Press a thumb into the ball of the baby's foot, just behind the toes. The toes curl down around it.
Timeline: fades around 9 to 12 months — later than the palmar grasp because the legs and feet develop later than arms and hands.
The Babinski Reflex
Stroke the outer edge of the sole from heel to toe with a key or finger. The big toe extends upward (dorsiflexes), the other toes fan outwards.
Timeline: present from birth. Disappears by 12 to 18 months as the corticospinal tracts myelinate.
The funny thing about Babinski: the same response in an adult is an abnormal neurological sign — it indicates damage to the corticospinal tract above the lower spinal cord. In infants, that pathway isn't yet fully myelinated, and the response is normal. The same neuroanatomy gives different significance at different ages.
Flags: Babinski persisting past 18 months is investigated.
The Stepping Reflex
Hold the baby upright with their feet just touching a flat surface. They make alternating stepping movements, as if walking.
Timeline: prominent in the first 6 to 8 weeks, then fades. Returns later as voluntary walking develops, but is not the same neurological program.
Curious fact: practising the stepping reflex daily does not lead to earlier walking, despite a small influential 1972 study suggesting it might. Replication and meta-analysis have not supported the claim. Walking is gated by motor cortex maturation and balance development, not by reflex practice.
The Asymmetric Tonic Neck Reflex (Fencing Reflex)
Turn the baby's head to one side while they are lying on their back. The arm on the side the head is facing extends; the opposite arm flexes. Looks like a fencer's en garde stance.
Timeline: prominent from about 1 month, fades by 4 to 6 months.
Why it matters: persistent ATNR is one of the more frequently flagged primitive reflexes in conditions like cerebral palsy, where it interferes with rolling, midline play, and reaching across the body.
The Galant Reflex
Stroke down one side of the spine from shoulder blade to hip. The baby's hips swing toward the stroked side.
Timeline: fades by 3 to 6 months.
What This All Adds Up To
Reflexes are doing real work in the first months — feeding, soothing, attracting attention. They also let clinicians make a fast assessment of the nervous system without needing scans or sophisticated equipment. Symmetric, present-on-time, fading-on-time reflexes mean the relevant neural pathways are intact and the cortex is maturing on schedule.
What gets investigated:
- Asymmetry — one side different from the other
- Absence at birth in a term baby
- Persistence beyond the expected window
- Exaggeration or unusual quality
These findings prompt referral to community paediatrics or, in obvious neurological situations, urgent assessment.
What does not need investigation:
- The Moro itself, when it happens at expected times — it is a feature, not a problem
- The fading of reflexes on schedule — that is voluntary control developing
- A baby who startles a lot — newborn nervous systems are noisy; a sensitive Moro is normal
The unhelpful corner of this topic: a number of "primitive reflex retention" theories have circulated in alternative therapy circles, claiming that childhood behavioural and learning difficulties are caused by un-integrated infant reflexes that can be "reset" with specific exercises. The evidence base for these claims is poor. Clinicians do screen for retained reflexes when there is genuine neurological concern, but the wider concept has not been supported by rigorous trials. If a child is being assessed, NHS paediatric pathways are the appropriate route.
Key Takeaways
Newborns come pre-programmed with a set of reflexes — Moro (startle), rooting, sucking, palmar grasp, Babinski, stepping — that are run by the brainstem and lower brain structures before the cortex takes over. Each reflex has an expected timeline: the Moro fades by 4–6 months, rooting and sucking integrate by 4–6 months, palmar grasp by 4–6 months, the Babinski sign persists up to 12–18 months. The reflexes serve real purposes (rooting and sucking for feeding) and serve as a quick neurological check at birth — symmetric and present is reassuring; absent or asymmetric prompts assessment. The Moro is the reason swaddling helps newborns sleep — it stops the startle from waking them between sleep cycles.
