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Cervical Length Measurement (Ultrasound)

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

This test measures the length of your cervix using ultrasound, often done during pregnancy to assess risk of preterm labor.

Quick summary

["Your cervical length helps determine if you’re at higher risk for early delivery."]

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

Key facts at a glance

LOINC
11961-0
Short code
Cervix Length US.meas
Synonyms
Cervix 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 It’s Done

A healthcare provider may recommend this test if you’re at higher risk for preterm labor, such as due to a history of early deliveries, cervical shortening, or certain medical conditions. It’s also used to monitor high-risk pregnancies where cervical length changes could signal complications.

How It Works

A trained technician uses ultrasound waves to create an image of your cervix. The device measures the distance from the cervix’s opening to the top of the uterus, typically expressed in millimeters.

What to Expect

You’ll lie on your back on an exam table, with a gel applied to your abdomen. The technician places a small device (transducer) on your belly to capture images. The process is quick and painless, similar to a standard ultrasound.

Preparation

No special preparation is needed. You may need to drink water beforehand to help your bladder stay full, which can improve image clarity.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Cervix Length Check

Frequently asked questions

Why is cervical length measured during pregnancy?
Cervical length is measured to assess the risk of preterm birth, especially in women with a history of early deliveries or other risk factors. It helps guide whether additional monitoring or preventive measures are necessary.
What does a low cervical length mean?
A shorter cervical length (typically below 25 mm) may indicate an increased risk of preterm labor. Your healthcare provider will discuss next steps, such as closer monitoring or interventions, based on your specific situation.
Is cervical length testing painful?
No, cervical length testing is painless. You may feel a slight pressure or discomfort from the ultrasound gel, but the procedure itself does not cause pain.
  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