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Fetal Head Circumference (measured from gestational age-specific reference data)

Published: August 9, 2026Updated: August 16, 2026

This test measures the size of your baby’s head during pregnancy to help track growth and development.

Quick summary

["A head circumference check helps monitor fetal development and identify potential growth concerns early."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
33174-4
Short code
Fet Head Circum from GA.Chitty94
Synonyms
Fet Head Circum from GA.Chitty94
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
us-estimated-from-chitty
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why is this test important during pregnancy?

Your healthcare provider uses this measurement to compare your baby’s head size against standard growth curves for your expected due date. It helps assess whether your baby is growing at a healthy rate and can signal early signs of conditions like intrauterine growth restriction or other developmental issues.

How is this test performed?

This is not a blood or urine test but a measurement taken during prenatal ultrasounds. A trained technician uses a special tool to wrap around your baby’s head while in the womb to record the circumference.

What does a head circumference result mean?

Results are compared to gestational age-specific reference ranges. A larger-than-expected head circumference may suggest conditions like polyhydramnios, while a smaller measurement could indicate potential concerns that may require further evaluation.

What might affect this measurement?

Factors such as gestational age, fetal position, and maternal health (e.g., preeclampsia) can influence the results. Your provider will consider these alongside other prenatal data for a full assessment.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Gestational Age Head Circumference (GA Hc)

Frequently asked questions

Will this test hurt my baby?
No, this is a non-invasive measurement taken during an ultrasound, which is a safe and painless procedure for both you and your baby.
How often will I have this test?
Your provider may request this measurement during routine prenatal ultrasounds, typically at specific intervals such as 12–24 weeks of pregnancy, depending on your individual care plan.
What if my head circumference is outside the normal range?
If results are outside expected ranges, your healthcare team will discuss findings with you and may recommend further testing or monitoring to ensure your baby’s health and development are on track.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy