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Fetal alpha-fetoprotein (AFP) measured in maternal serum or plasma

Published: August 9, 2026Updated: August 17, 2026

Alpha-fetoprotein (AFP) is a protein produced by the fetus that helps monitor certain prenatal conditions, including neural tube defects and other birth abnormalities.

Quick summary

["AFP screening helps identify risks for birth defects during pregnancy."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
62245-6
Short code
nRBC Bld Fetus Auto-Rto
Synonyms
nRBC Bld Fetus Auto-Rto
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Ref low
4.2
Ref high
5.9
Critical range
2 N/A – 7 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
automated-count
CPT
85041
SNOMED
900000000000003001
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may recommend an AFP test during the first or second trimester to check for potential birth defects, such as spina bifida or other neural tube defects. It may also be used to assess other conditions like Down syndrome or other chromosomal abnormalities, depending on the context of your pregnancy.

How Is the Sample Collected?

A blood sample is taken from your arm, usually between weeks 14 and 22 of pregnancy. The blood is processed to separate the serum or plasma for testing.

What Does the Test Measure?

The test measures the concentration of AFP in your blood. AFP levels can vary based on gestational age, fetal health, and potential underlying conditions.

What Are the Possible Results?

Results are interpreted in the context of your pregnancy timeline and other prenatal tests. Low or high AFP levels may signal increased risk for certain birth defects or other conditions, prompting further evaluation.

Reference range

Adult males: 4.2-5.9; Females: 3.8-5.1 x 10^12/LN/A

Specimen: whole-blood

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

AFP Screening

Frequently asked questions

What does an AFP test measure in pregnancy?
An AFP test measures alpha-fetoprotein, a protein produced by the fetus that helps assess risks for birth defects like neural tube defects.
How soon after pregnancy can I get an AFP test?
AFP testing is typically done between weeks 14 and 22 of pregnancy, but timing can vary based on clinical guidelines and your healthcare provider’s recommendations.
Can AFP levels change throughout pregnancy?
Yes, AFP levels fluctuate with gestational age and fetal development. Your results will be compared to expected ranges for your specific trimester.
  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 17, 2026. · Read our editorial policy