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Test ID 1STT1 First Trimester Maternal Screen, Serum

Specimen Required

Ordering Guidance

This test does not screen for neural tube defects. If risk assessment for neural tube defects is desired, collect specimen between 15 weeks, 0 days and 22 weeks, 6 days for an AFP single marker screen, MAFP1 / Alpha-Fetoprotein (AFP), Single Marker Screen, Maternal, Serum.


QUAD screening (QUAD1 / Quad Screen (Second Trimester) Maternal, Serum is not recommended following first-trimester screening.


For more information on testing options, see Prenatal Aneuploidy Screening and Diagnostic Testing Options

Necessary Information

Approval to send specimen for first-trimester screening is required and may take up to 5 business days to complete. Nuchal translucency (NT) measurements are only accepted from NT-certified sonographers. Do not send specimen to Mayo Clinic Laboratories if the sonographer is not NT-certified or before completing the application process. See Maternal Screening: Sonographer Approval Process link or complete the NT/CRL Data for First Trimester/Sequential Maternal Screening.

Specimen Required

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions: Centrifuge and aliquot serum into plastic vial within 2 hours of collection

Additional Information:

1. Blood draw and ultrasound must be completed between 10 weeks, 0 days and 13 weeks, 6 days, which corresponds to a crown-rump length (CRL) range of 31 to 80 mm.

2. Initial or repeat testing is determined in the laboratory at the time of report and will be reported accordingly. To be considered a repeat test for the patient, the testing must be within the same pregnancy and trimester, with interpretable results for the same test and both tests are performed at Mayo Clinic.

Useful For

Prenatal screening for trisomy 21 (Down syndrome) and trisomy 18

Method Name

Immunoenzymatic Assay

Reporting Name

First Trimester Maternal Screen

Specimen Type


Specimen Minimum Volume

0.75 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 14 days
  Frozen  90 days
  Ambient  7 days

Reference Values


Calculated screen risks <1/230 are reported as screen negative.

Risks ≥1/230 are reported as screen positive.



Calculated screen risks <1/100 are reported as screen negative.

Risks ≥1/100 are reported as screen positive. A numeric risk for trisomy 18 risk is provided with positive results on non-diabetic, non-twin pregnancies.

An interpretive report will be provided.

Day(s) Performed

Monday through Friday

Report Available

4 to 6 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
1STT1 First Trimester Maternal Screen 49086-2


Result ID Test Result Name Result LOINC Value
26428 Recalculated Maternal Serum Screen 43995-0
601798 Results Summary 50679-0
26434 Down Syndrome Screen Risk Estimate 43995-0
26435 Down Syndrome Maternal Age Risk 49090-4
26436 Trisomy 18 Screen Risk Estimate 43994-3
26426 PAPP-A 48407-1
601515 PAPP-A MoM 76348-2
26427 THCG 32166-1
601516 THCG MoM 32166-1
NT_ NT 49035-9
601517 NT MoM 49035-9
NT_B NT Twin 49035-9
601518 NT Twin MoM 49035-9
26437 Interpretation 49588-7
26439 Recommended Follow Up 80615-8
26438 Additional Comments 48767-8
26411 Specimen Collection Date 33882-2
26412 Maternal Date of Birth 21112-8
26429 Calculated Age at EDD 43993-5
26413 Maternal Weight 29463-7
26880 Maternal Weight 29463-7
IDD_ Insulin dependent diabetes 44877-9
B_RCE Patient Race 21484-1
SMKN1 Current cigarette smoking status 64234-8
DT3 Scan Date 34970-4
CRL1 CRL 11957-8
CRL2 CRL Twin 11957-8
26430 GA on Collection by U/S Scan 11888-5
NUMF Number of Fetuses 55281-0
CHOR Number of Chorions 92568-5
IVF IVF 47224-1
PRHX Prev Down (T21) / Trisomy Pregnancy 53826-4
INTL1 Initial or repeat testing 86955-2
SONON Sonographer Name 49088-8
SONOC Sonographer Code No LOINC Needed
SONOD Sonographer Reviewer ID 49089-6
DRPH1 Physician Phone Number 68340-9

NY State Approved