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Fetal Thorax Circumference Measured via Ultrasound

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

This test measures the size of your baby’s chest using ultrasound during pregnancy to monitor growth and development.

Quick summary

["An ultrasound check helps ensure your baby is growing as expected."]

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

Key facts at a glance

LOINC
11990-9
Short code
Fet Thorax Circum US.traced
Synonyms
Fet Thorax Circum US.traced
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-traced
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?

Your healthcare provider may order this test to assess fetal growth patterns, detect potential issues like abnormal development, or monitor high-risk pregnancies. It’s often performed during routine ultrasounds between weeks 18 and 32 of pregnancy.

What Happens During the Test?

You’ll lie on an exam table while a technician applies a gel to your abdomen. A handheld device (transducer) sends sound waves to create images of your baby’s chest. The measurement is taken from the widest part of the fetal thorax.

What Does the Result Mean?

The result compares your baby’s chest size to expected growth curves. Small or large measurements may prompt further evaluation, such as additional ultrasounds or genetic testing, depending on your healthcare provider’s assessment.

Are There Any Risks?

Ultrasound is generally safe and has no known risks. However, you may feel slight pressure or discomfort from the gel, but the procedure itself is painless.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Fetal Chest Circumference (Ultrasound)

Frequently asked questions

Why did my provider request this test?
Your provider may have noted concerns about fetal growth, a history of pregnancy complications, or other risk factors that warrant monitoring. This test helps track your baby’s development safely and promptly.
What if my baby’s chest circumference is smaller or larger than expected?
If the measurement falls outside typical ranges, your provider may recommend closer monitoring or additional tests (e.g., Doppler ultrasound for blood flow). Always discuss results with your healthcare team.
Can I eat or drink before this test?
No special preparation is needed. You can eat, drink, and move around as usual. Ultrasound tests do not 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