Small Head (Microcephaly) in Babies
Content reviewed against published CDC, AAP, WHO guidelines
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Microcephaly is defined as a head circumference below the 3rd percentile or more than 2 standard deviations below the mean for age and sex. It can be congenital (present at birth) or acquired (develops after birth). While some babies simply have smaller heads genetically, microcephaly can indicate problems with brain growth and development.
Key takeaways
- Microcephaly is defined as a head circumference below the 3rd percentile or more than 2 standard deviations below the mean for age and sex.
- Most common cause: Constitutional (familial small head with normal development)
- Emergency: Seizures in a baby with a small head
- Home care: Track head circumference monthly on a growth chart
Possible Causes
When to Seek Help
Emergency — Call 911 or go to ER:
- Seizures in a baby with a small head
- Sudden unresponsiveness or lethargy
- Severe feeding difficulty with dehydration signs
Urgent — See doctor today:
- Head circumference dropping across percentile lines over weeks
- Small head with missed developmental milestones and abnormal tone
- Ridged suture lines preventing normal head growth
- Microcephaly detected at birth with neurological concerns
Same-day appointment:
- Head circumference just below 3rd percentile at routine visit
- Small head noted with mild developmental concerns
- Small head with parental concern about milestones
Monitor at home:
- Parents have small heads and baby is developing normally
- Head tracking steadily along a low percentile with normal milestones
- Mild smallness consistent with overall small stature
By Age
0-3 months
Normal: Newborn head circumference varies; at birth, normal range is approximately 32-37 cm. A small baby may have a proportionally small head. Parental head size matters.
Worry if: Head circumference below 3rd percentile with abnormal neurological exam, failure to grow at expected rate, ridged or raised suture lines, or missing developmental milestones.
3-12 months
Normal: Head should grow approximately 1 cm per month. If tracking along a low percentile with normal milestones, may be constitutional.
Worry if: Head growth falling away from growth curve, delayed motor or cognitive milestones, seizures, feeding difficulties, or unusual head shape from fused sutures.
1-3 years
Normal: Head growth slows to about 2 cm per year. Steady tracking along a low percentile with normal development may be benign.
Worry if: Developmental regression, no head growth over several months, progressive spasticity, or new onset seizures.
Home Care
- Track head circumference monthly on a growth chart
- Monitor and document developmental milestones
- Measure parental head circumferences for comparison
- Provide tummy time and developmental stimulation
- There is no home treatment for microcephaly—early intervention services may be recommended
- Keep records of any concerns to discuss at well-child visits
Frequently asked questions
What causes small head (microcephaly)?
When is this an emergency?
What can I do at home?
When should I call the doctor?
Sources
All content follows our editorial policy and is reviewed against published clinical guidelines.
2,705 evidence-based guides6 authoritative medical sources
Related Symptoms
Bottom line
Most cases of small head (microcephaly) in babies are not emergencies. However, seek immediate care if seizures in a baby with a small head.
Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.