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Maternal Serum Alpha-Fetoprotein (AFP), Weight-Adjusted Multiples of the Median (MoM)

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

A prenatal blood test that measures AFP and adjusts the result for maternal weight, comparing it with expected levels for the pregnancy.

Quick summary

["This is a prenatal screening result, not a diagnosis, and an abnormal value usually requires further testing."]

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

Key facts at a glance

LOINC
43997-6
Short code
AFP Wt adj MoM SerPl
Synonyms
AFP Wt adj MoM SerPl
Category
liver
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0
Ref high
10
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82105
SNOMED
394971007
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

What is this test?

Maternal serum alpha-fetoprotein (AFP) is a blood test used during pregnancy. The result is adjusted for maternal weight and reported as multiples of the median, or MoM, to compare it with the AFP level expected for the current stage of pregnancy.

Why might I need this test?

This test may be used as part of prenatal screening for conditions such as open neural tube defects and trisomy 21. It is usually interpreted together with other screening information and does not confirm a fetal condition by itself.

How is the test performed?

A blood sample is drawn from a vein and sent to a laboratory. The laboratory measures AFP in the serum and converts the result into a weight-adjusted MoM value.

How do I prepare for the test?

Fasting is generally not required for this test. Follow the timing and preparation instructions provided by your prenatal care team, and tell the laboratory if you are pregnant or have had a recent blood transfusion.

Reference range

Normal: <10 ng/mLN/A

Specimen: serum

No special preparation required. For PSA, avoid sexual activity for 24-48 hours before the test.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Weight-adjusted maternal serum AFP, MoM

Frequently asked questions

Does an abnormal AFP MoM mean my baby has a condition?
No. This is a screening test, so an abnormal result indicates that more evaluation may be needed but does not confirm a fetal condition.
What does weight-adjusted MoM mean?
MoM compares the measured AFP level with the expected level for the pregnancy, while weight adjustment accounts for differences in maternal weight that can affect AFP concentration.
Will I need another test if the result is abnormal?
Often, yes. A clinician may recommend targeted ultrasound, genetic counseling, or a diagnostic test to obtain more information.
  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