A baby's first reflexes are not personality. They are the brainstem doing its job before the cortex is ready. Stroke a newborn's cheek and they root toward your finger; let their head drop suddenly and the arms fling out, then return to the midline. Each of these patterns has a window in which it should appear, and a window in which it should disappear — and clinicians read both windows as a quick neurological screen. Healthbooq covers the reflexes parents will see and the ones the GP or health visitor is checking for.
What Primitive Reflexes Are
Primitive reflexes are stereotyped motor responses generated by the brainstem and spinal cord, without input from the cerebral cortex. The cortex at birth is large but immature: most of its connections are still being wired in the first months and years. Reflexes are what runs the show until cortical control comes online.
As the cortex matures, it inhibits the primitive responses — they "integrate" rather than vanish, becoming inaccessible as automatic movements while voluntary control replaces them. If the cortex doesn't develop on schedule (as in cerebral palsy, hypoxic-ischaemic injury, or some genetic conditions), reflexes may persist or re-emerge. That's why the timing of disappearance is as clinically informative as the timing of appearance.
Where the Checks Happen
Two NHS checkpoints assess reflexes routinely:
- The newborn and infant physical examination (NIPE) — performed within the first 72 hours after birth. Includes a check of the Moro, palmar grasp, rooting and sucking, plantar response, and an assessment of muscle tone and symmetry.
- The 6–8-week infant review — performed by a GP. Reflexes that should still be present (rooting weakening, grasp weakening but present, Moro still present) and tone are reassessed.
Outside these formal checks, parents who notice asymmetry — one arm moving differently from the other in a startle, for example — should mention it at the next health visitor appointment rather than waiting.
The Timeline, Reflex by Reflex
Moro (startle). Triggered by a sudden change in head position, a loud noise, or a sensation of falling. The arms abduct (fling wide), fingers spread, and then the arms come back toward the midline, often with a cry. Present from birth; integrates by 4–6 months. An absent Moro at birth raises concern about CNS depression or sedation. An asymmetric Moro — one arm extending less than the other — points toward a fractured clavicle, brachial plexus injury (Erb's palsy), or hemiparesis on the weaker side, and warrants assessment.
Rooting. Stroke the corner of the mouth or cheek; the baby turns toward the stimulus and opens the mouth. Present from birth; integrates by 3–4 months as voluntary head turning takes over. Useful for breastfeeding positioning in the first weeks. Weak or absent rooting can affect feeding and warrants review.
Sucking. A finger or nipple on the palate triggers rhythmic sucking. Functional from around 32 weeks gestation; integrates around 3–4 months as feeding becomes a more voluntary activity. A weak or uncoordinated suck in a term newborn — particularly when paired with poor weight gain — raises concern about prematurity, hypotonia, or neurological difficulty.
Palmar grasp. Pressure on the palm causes the fingers to curl tightly. A newborn's palmar grasp is strong enough to support some of their own body weight, although this is not safely tested. Present from birth; integrates by 5–6 months, making way for voluntary, intentional grasping. Persistence past 6 months is associated with later difficulty developing a pincer grip.
Plantar grasp. Pressure on the ball of the foot makes the toes curl downward. Present from birth; integrates by around 9–12 months, allowing the foot to flatten for standing and walking.
Stepping (walking) reflex. Held upright with the soles touching a firm surface, the baby makes alternating stepping movements. Present from birth; integrates by around 2 months, then re-emerges months later as voluntary walking around 9–15 months. This reflex is unrelated to early walking ability — there is no value in "training" it.
Babinski. Stroke the outer edge of the sole from heel to toe; the big toe extends upward and the other toes fan out. Normal until about 12–18 months. After that age, an upgoing Babinski (a positive Babinski sign) is abnormal and indicates upper motor neuron pathology, so it's pursued differently. In an infant, it's expected.
Asymmetric tonic neck reflex (ATNR / "fencer"). Turn the head to one side; the arm and leg on that side extend, the opposite arm flexes. Present from birth; integrates by 4–6 months. Persistent ATNR can interfere with rolling, midline reaching, and later with crossing the midline for tasks like reading, writing, and bilateral coordination.
What Counts as a Red Flag
The patterns clinicians watch for:
- Absence at birth of expected reflexes — particularly the Moro and the suck — suggests CNS depression, sedation, hypoxic-ischaemic injury, or significant prematurity.
- Asymmetry — one arm or leg responds noticeably less than the other. Birth-related causes (clavicular fracture, brachial plexus injury) are common; intracranial causes are less common but more serious.
- Persistence past the integration window — a strong Moro after 6 months, an ATNR after 6 months, a clear Babinski sign after 18 months. These point toward delayed cortical inhibition and warrant developmental review.
- Re-emergence after integration — a previously integrated reflex returning in an older baby is unusual and should be assessed.
When to Mention It
Most parents don't need to test reflexes themselves; the routine checks cover this. Raise it at the next health visitor or GP appointment, or sooner, if you notice:
- One side of the body consistently responding differently from the other
- A baby who's hard to startle, generally floppy, or unusually stiff
- A reflex you've watched for weeks that's still as strong at 7–8 months as it was at 1 month
- Feeding difficulties that fit a weak suck or poor coordination of suck-swallow-breathe
The signals are usually subtle, and the routine examinations are designed to catch them. If something doesn't sit right, it's worth a conversation rather than a wait-and-see.
Key Takeaways
Primitive reflexes are involuntary motor responses run by the brainstem and spinal cord. They appear during the third trimester, are checked at the first 72-hour newborn examination (NIPE) and again at the 6–8-week review, and are expected to integrate on a predictable schedule as the cerebral cortex takes over voluntary movement. The clinically meaningful signals are absence at birth, asymmetry between left and right, and persistence past the integration window — for example, a Moro that's still strong after 6 months or a Babinski sign after 18 months. Each reflex has its own timeline, and clinicians use those timelines as a low-cost neurological screen.
