A newborn arrives with a small library of pre-installed software — automatic responses that don't need teaching, run at brainstem level, and disappear in a roughly predictable order as the cortex comes online. Watching them turn up on schedule and then fade on schedule is one of the simplest ways doctors check that the wiring is in order. For a wider view, see our complete guide to child health.
What a Reflex Actually Is
A reflex is an involuntary motor response to a specific stimulus, hard-wired through the spinal cord and brainstem rather than the cerebral cortex. The newborn cortex isn't yet running the show; it spends the first months of life laying down myelin, refining connections, and gradually taking over. As cortical control comes online, the cortex actively suppresses the primitive reflexes — which is why the disappearance of a reflex is as informative as its presence.
Two patterns matter clinically:
- Asymmetry. A Moro that's present on one side and absent on the other usually points to a problem with the limb itself, not the brain — most commonly a brachial plexus injury sustained during a difficult delivery (Erb's palsy from a stretching of C5–C6 nerve roots, classic after shoulder dystocia). It can also be a clavicle fracture, which heals well but is sore on movement.
- Persistence. A reflex that's still strong months past the expected fade point can suggest the cortex isn't suppressing it — which is one of the early signs sometimes seen in cerebral palsy or other central neurological conditions.
A single absent reflex in an otherwise well baby usually doesn't mean a great deal; the pattern across reflexes, plus muscle tone, posture, and how the baby uses their body, is what the clinician is reading.
The Reflexes Worth Knowing
Moro (the startle)
The most theatrical of the lot. Triggered by a sudden change in head position — letting the head drop a few centimetres while supporting the body, a loud noise, or the sensation of falling. The baby throws the arms out wide with the fingers fanned (extension), then brings them back in towards the chest as if to grip something (flexion), often with a cry.
- Present: from birth (well established by 28–32 weeks gestation).
- Fades: by 3–6 months.
- Concerns: absent at birth, asymmetrical, or still strong past 6 months. An absent Moro on one arm in particular raises immediate suspicion of brachial plexus injury and warrants assessment before discharge from the maternity unit.
Rooting
Stroke a finger along the cheek towards the corner of the mouth. The baby turns the head toward the touch and opens the mouth. It's the reflex that helps a newborn locate the breast — useful in the first hours of life, and one of the things midwives use when they encourage skin-to-skin contact for the first feed.
- Present: from birth (28 weeks gestation onwards).
- Fades: by 3–4 months, as the baby starts to turn the head voluntarily and recognise visual cues for feeding.
Sucking and the Suck-Swallow-Breathe Coordination
Place a clean finger or nipple in the mouth and the baby sucks rhythmically. What looks like a single reflex is actually a tightly coordinated sequence — suck, swallow, breathe — that has to align for safe oral feeding.
- Sucking reflex: present from about 32 weeks gestation, but the coordination with breathing isn't reliable until around 34 weeks. This is why babies born before 34 weeks often need NG (nasogastric) tube feeding initially, even when they look big enough to feed orally.
- Fades: the involuntary reflex around 4 months; voluntary sucking continues.
A weak or uncoordinated suck in a term baby can indicate prematurity (in a baby small for dates), neurological issue, or — surprisingly often — a tongue-tie that hasn't been picked up.
Palmar Grasp
Place your finger across the baby's palm. The fingers close firmly around it. Strong enough that you can sometimes lift a newborn partially off the surface by their grip, though you obviously wouldn't.
- Present: from birth.
- Fades: by 5–6 months, replaced by voluntary grasp using the whole hand, and later — around 9 months — by the pincer grip between thumb and index finger.
Parents often read this as deliberate affection; it isn't yet. The deliberate version arrives later and is much more selective.
Plantar Grasp
Stroke the sole of the foot just behind the toes. The toes curl down, as if trying to grip. Mechanically the foot version of the palmar grasp.
- Present: from birth.
- Fades: by 9–12 months, as walking preparation begins.
Stepping
Hold the baby upright with the soles touching a flat surface and tilt the body slightly forward. The baby makes alternating stepping movements. This isn't proto-walking — it's a brainstem reflex, and it disappears long before real walking begins.
- Present: from birth.
- Fades: by around 2 months.
- Reappears: as voluntary walking, typically between 9 and 18 months.
The gap between the reflex and real walking — six to twelve months — is one of the cleanest examples of cortical takeover.
Tonic Neck (the "fencing" posture)
With the baby on their back, turn the head gently to one side. The arm and leg on the side the face is pointing extend; the arm and leg on the opposite side flex. The result looks like a fencing en garde. It's thought to support hand-eye coordination and the development of reaching towards an object the baby is looking at.
- Present: from birth.
- Fades: by 5–7 months.
A persistently strong tonic neck reflex past 6 months can interfere with rolling over and reaching across the midline, which is one of the things therapists watch in babies being assessed for cerebral palsy.
Babinski (the plantar response)
Stroke the sole of the foot from heel up the outer edge towards the toes. In an infant, the big toe goes up and the smaller toes fan outwards. In an adult, that same response signals damage to the corticospinal tract. The difference is myelination — once the descending pathways from the cortex are properly myelinated, the response flips.
- Present: from birth.
- Fades: between 12 and 24 months.
When a Reflex Finding Should Prompt a Closer Look
A few specific patterns that warrant raising with your GP, health visitor, or the assessing midwife:
- A Moro that's clearly weaker on one arm than the other, especially after an instrumental delivery or shoulder dystocia — early physiotherapy referral matters for brachial plexus recovery.
- Any reflex that seems clearly absent on one side (rooting only on the left, palmar grasp only on the right).
- Reflexes that are still robust well past their expected fade — for example, a strong Moro at 8 months, or stepping that's still present at 4 months.
- A baby who is generally floppy ("hypotonic") or unusually stiff ("hypertonic"), with or without specific reflex changes — tone is more important than any individual reflex.
- A rooting/sucking pattern that's weak enough to interfere with feeding and weight gain.
Reflexes are checked formally at the newborn examination (NIPE — Newborn and Infant Physical Examination, usually within 72 hours of birth) and again at the 6–8 week GP review, but you don't need to wait for an appointment if something is worrying you. Most things picked up via reflex testing are mild and resolve on their own; the small number that benefit from earlier intervention — birth-related nerve injuries, central tone problems — do better the sooner they're seen.
Key Takeaways
Primitive reflexes are wired through the brainstem and spinal cord, not the cortex — they appear at predictable points before birth, fade as the cortex takes over voluntary control, and their disappearance is itself a developmental sign. Approximate fade-out: Moro by 3–6 months, rooting by 3–4 months, palmar grasp by 5–6 months, plantar grasp by 9–12 months, stepping by 2 months (then re-emerges as voluntary walking around 12 months), tonic neck by 5–7 months, Babinski up to 12–24 months. Asymmetry — present on one side, absent on the other — is the single most important warning sign and may indicate brachial plexus injury or central pathology. Reflexes are checked at the newborn (NIPE) examination, the 6–8 week GP review, and onwards in routine developmental assessment.
