Fetal Body Weight Percentile Based on Gestational Age
This test compares your baby’s estimated weight to the average weight of babies at the same gestational age. It helps assess whether the baby is on track for healthy growth during pregnancy.
["This test helps monitor fetal development and identify potential growth concerns early."]
Key facts at a glance
- LOINC
- 11766-3
- Short code
- Fet Bdy weight Prctl Per est GA
- Synonyms
- Fet Bdy weight Prctl Per est GA
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- per-estimated-gestational-age
- 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
How This Test Works
Your healthcare provider uses ultrasound imaging to estimate your baby’s weight. The test compares this estimate to a standard growth curve for babies at your specific gestational age, providing a percentile ranking (e.g., 50th percentile means your baby’s weight is average for that stage).
Why It’s Done
This test is typically performed during prenatal ultrasounds, especially if there are concerns about fetal growth, such as a history of gestational diabetes, high blood pressure, or previous small-for-gestational-age babies. It helps ensure your baby is growing appropriately.
What to Expect
You’ll likely have a standard prenatal ultrasound, which involves lying on your back with a gel applied to your abdomen. The ultrasound technician moves a handheld device (transducer) over your belly to measure your baby’s size and estimate weight. The process is painless and usually takes about 20–30 minutes.
Factors That May Affect Results
Several factors can influence fetal weight estimates, including the accuracy of the ultrasound machine, your baby’s position during the scan, and gestational age. If your baby is in a difficult position (e.g., curled up), the estimate may be less precise.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
A low fetal weight percentile may signal potential growth restrictions, which could require further monitoring or interventions (e.g., dietary adjustments, closer prenatal care). A high percentile may raise questions about placental function or other factors, though it doesn’t always indicate a problem. Always discuss results with your healthcare provider for personalized guidance.
Short name
Fetal Weight Percentile
Frequently asked questions
When will I get my results?
What does a low or high percentile mean?
Can diet or lifestyle changes affect this test?
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