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Fetal Head Circumference Measurement

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

This test measures the circumference of a baby’s head during pregnancy to monitor fetal growth and development. It helps healthcare providers track progress and identify potential concerns early.

Quick summary

["A fetal head circumference check ensures your baby grows at a healthy rate during pregnancy."]

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

Key facts at a glance

LOINC
11984-2
Short code
Fet Head Circum US.meas
Synonyms
Fet Head Circum US.meas
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-measured
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 Done?

Doctors may order a fetal head circumference measurement during prenatal ultrasounds to assess fetal growth, detect abnormalities, or monitor conditions like intrauterine growth restriction. It’s often used alongside other measurements like abdominal circumference and biparietal diameter.

What to Expect During the Test

This test is typically performed as part of a routine ultrasound. You’ll lie on your back, and a technician will use a special probe to measure the head’s outer edge. It’s quick, painless, and doesn’t require preparation.

How Is the Result Interpreted?

Results are compared to standard growth charts for gestational age. While a single measurement isn’t diagnostic, repeated checks help track trends. Abnormal results may prompt further evaluation, such as additional ultrasounds or specialist referrals.

Common Reasons for Testing

Fetal head circumference may be checked if you have risk factors (e.g., high blood pressure, diabetes) or if your baby hasn’t grown as expected. It can also help confirm gestational age in early pregnancy.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Regular fetal head circumference measurements are crucial for identifying early signs of fetal growth issues, such as macrosomia (large baby) or small-for-gestational-age (SGA) conditions. Early detection allows for timely interventions, like adjusting medication or planning delivery timing, to optimize outcomes.

Short name

FHC

Frequently asked questions

What does a fetal head circumference test measure?
This test measures the outer perimeter of your baby’s head, which helps assess growth and development during pregnancy. It’s part of a broader ultrasound evaluation.
How often is this test done?
The frequency depends on your pregnancy status. Typically, it’s checked during routine ultrasounds, often starting around the 18th–22nd week and continuing if needed.
Can I eat or drink before this test?
No special preparation is needed. You can eat, drink, or take medications as usual. The ultrasound probe won’t require fasting.
  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