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Fetal Fibular Length Measurement (Ultrasound)

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

This test measures the length of a fetal fibula (one of the long bones in the lower leg) using ultrasound imaging. It helps assess fetal bone development during pregnancy.

Quick summary

["This measurement supports early detection of potential fetal growth concerns."]

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

Key facts at a glance

LOINC
53679-7
Short code
Fet Fibula-R Length US.meas
Synonyms
Fet Fibula-R Length 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 during prenatal ultrasounds, particularly in the second trimester, to evaluate fetal bone development. It can help identify conditions like fetal growth restriction or skeletal abnormalities early on.

What to Expect During the Test

You’ll lie on your back on an exam table with a gel applied to your abdomen. A transducer (probe) is placed on your skin to send sound waves to the fetus. The ultrasound machine creates images of the fibula to measure its length.

Fetal Development and Bone Health

Fetal fibular length is part of broader assessments of fetal skeletal development. While this specific measurement alone isn’t diagnostic, it may be used alongside other ultrasound findings to guide further evaluation.

What This Test Might Indicate

Abnormal measurements could signal potential issues like fetal growth delays or skeletal dysplasia, but results are interpreted in context with other prenatal tests and clinical findings.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Fetal Bone Length

Frequently asked questions

How often will I need this test?
This test is typically performed once during routine prenatal ultrasounds, often around 18–22 weeks of pregnancy, unless additional monitoring is recommended by your provider.
What if my fibular length is different from what’s expected?
Your provider will discuss any deviations with you during the ultrasound. While individual variation exists, repeated concerns may prompt further evaluation, such as additional imaging or genetic counseling.
Does this test require fasting or special preparation?
No special preparation is needed. You can eat and drink normally before the test, as it’s a non-invasive ultrasound procedure.
  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