Placental Alkaline Phosphatase (PLAP) Test

Published: July 31, 2026Updated: August 10, 2026

A blood test that detects placental alkaline phosphatase, a special protein made by the placenta during pregnancy, helping your healthcare team check how well the placenta is working and supporting your baby's growth and overall pregnancy health.

Quick summary

{"Measures placental alkaline phosphatase (PLAP) in maternal blood","Helps evaluate placental function and health during pregnancy","Used to monitor risk of pregnancy complications like preeclampsia","Typically performed in the second and third trimesters","Results indicate presence or absence of PLAP"}

Medically reviewed by WellAlly Editorial TeamLast reviewed August 10, 2026Editorial policy

Key facts at a glance

LOINC: 40793-2
Short code: PLAP
Synonyms: ALP Plac SerPl Ql
Category: chemistry
Sample: serum
Container: Serum separator tube (SST) or plain red top tube
Units: not specified
Ref low: 0
Ref high: 0.25
Fasting: false
Population: adult
Sex: all
Age range: ≥ 18 years
Method: Immunoassay (Chemiluminescence or ELISA)
CPT: 82150
SNOMED: 31316003
Specimen volume: 1.0-2.0 mL serum
Stability: Room temperature: 24-48 hours; Refrigerated (2-8°C): 5-7 days; Frozen (-20°C or below): several weeks. Avoid repeated freeze-thaw cycles.
Hemolysis max: 50
Lipemia max: 100
Icterus max: 20
TAT: 2–72 hours
Order: routine

What is this test?

The placental alkaline phosphatase (PLAP) test is a blood test that detects the presence of a specific enzyme produced by the placenta during pregnancy. Placental alkaline phosphatase is a protein made only by the placental tissue, and its detection in the mother's blood can provide important information about how well the placenta is functioning.

How is the test performed?

A healthcare provider will draw a small blood sample from a vein in your arm. The sample is then sent to a laboratory where it is analyzed for the presence of placental alkaline phosphatase. The test is typically performed during the second or third trimester of pregnancy as part of routine prenatal care or when specific pregnancy concerns exist.

Why is this test important?

The placenta is essential for providing oxygen and nutrients to your growing baby. By measuring PLAP levels, healthcare providers can get valuable information about placental health and function. Abnormal PLAP levels may indicate potential problems with the placenta that could affect pregnancy outcomes.

Reference range

Negativenot specified

Specimen: serum

No special preparation or fasting required

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

The PLAP test helps healthcare providers assess placental function and detect potential pregnancy complications. Low or absent PLAP levels may indicate placental insufficiency, where the placenta cannot adequately support the developing baby. This can be associated with conditions such as preeclampsia, intrauterine growth restriction (IUGR), or placental abruption. Elevated or abnormal PLAP levels may also warrant further investigation into placental health. This test is often used in conjunction with other prenatal tests to get a comprehensive picture of pregnancy health.

Frequently asked questions

Do I need to fast before the test?

No, you do not need to fast before the placental alkaline phosphatase test. You can eat and drink normally before the blood draw. However, always follow any specific instructions given by your healthcare provider.

Is the test safe during pregnancy?

Yes, the PLAP test is a simple blood test and is considered safe during pregnancy. It only requires a small blood sample and carries minimal risks, similar to any routine blood draw.

What do the results mean?

Results are typically reported as positive (PLAP is present) or negative (PLAP is not detected). A positive result indicates that placental alkaline phosphatase is being produced, suggesting placental function. Your healthcare provider will interpret your results in the context of your overall pregnancy and other test findings.

Will I need additional tests?

If your PLAP results are abnormal, your healthcare provider may recommend additional tests such as ultrasound to assess fetal growth and placental health, Doppler studies to check blood flow, or other blood tests to evaluate pregnancy complications.

Sources

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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 10, 2026. · Read our editorial policy