Measurement of transverse diameter of the fetal thorax (fetal ultrasound)
This test measures the width of your baby’s chest on an ultrasound during pregnancy. It helps healthcare providers assess fetal growth and development.
["This measurement supports early detection of potential growth concerns during pregnancy."]
Key facts at a glance
- LOINC
- 11864-6
- Short code
- Fet Thorax Diam transverse US.meas
- Synonyms
- Fet Thorax Diam transverse 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?
Your healthcare provider may order this test if they suspect your baby’s growth might be slower than expected. It’s often part of routine ultrasounds during mid-pregnancy (around 18–24 weeks) to monitor fetal development and identify any potential issues early.
How Is the Test Performed?
A trained ultrasound technician uses a gel and a handheld device (transducer) placed on your abdomen to create images of your baby. The technician measures the width of your baby’s chest area on the screen. The process is painless and typically takes about 20–30 minutes.
What Does the Result Mean?
The result is compared to standard growth charts for babies at your pregnancy’s stage. While no single measurement alone determines fetal health, repeated ultrasounds can track overall growth trends. If the width appears smaller than expected, further evaluation may be needed to rule out conditions like intrauterine growth restriction.
What Are the Risks or Side Effects?
There are no known risks to you or your baby from this test. You may feel slight pressure or discomfort from the gel, but it’s temporary.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: This measurement is critical for identifying potential fetal growth issues early. While a single measurement may not raise concerns, repeated ultrasounds help monitor overall fetal development. Abnormal findings may prompt additional testing, such as Doppler ultrasound for blood flow assessment or further imaging to investigate underlying causes.
Short name
Fetal Thorax Width (US)
Frequently asked questions
Will this test hurt?
How often will I need this test?
What if my baby’s chest width is smaller than expected?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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