Gestational Age at Onset of Symptoms (Serum/Plasma Substance Concentration)
This test measures the level of a substance in your blood to estimate how far along you are in pregnancy when you first became ill. It helps healthcare providers assess timing of symptoms relative to pregnancy progression.
["This test helps determine if illness onset aligns with early pregnancy stages."]
Key facts at a glance
- LOINC
- 81270-1
- Short code
- GA (weeks)--at onset of illness
- Synonyms
- GA (weeks)--at onset of illness
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 0
- Ref high
- 17
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- 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 This Test Matters in Pregnancy
During pregnancy, timing of symptoms can be critical for diagnosis and treatment planning. This test helps doctors understand whether your illness began before or after conception, which may influence decisions about care, monitoring, or potential risks to the pregnancy.
How the Test Works
A blood sample is taken to measure a specific marker (not named here) that changes predictably as pregnancy progresses. Advanced technology detects this marker’s concentration to estimate gestational age at symptom onset.
What to Expect Before the Test
No special preparation is needed. You may have a standard blood draw, often done in a clinic or lab. Tell your provider about any medications or recent illnesses to ensure accurate results.
What the Results Mean
Results provide a relative estimate (not a precise date) of when symptoms began compared to pregnancy timeline. For example, a result indicating early gestational age may suggest symptoms started before conception or very early in pregnancy.
Reference range
NCBI: NSE 0-17 ng/mLN/A
No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
Gestational Age at Illness Start (Serum)
Frequently asked questions
This test may be used in rare cases to investigate unexplained symptoms in pregnancy, such as early-onset infections or conditions requiring specialized care. It helps rule out or confirm timing-related factors in diagnosis.
How accurate is this test?
Can I fast before 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 17, 2026. · Read our editorial policy