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Test Code SEQU Sequential Maternal Screening, Part 1, Serum

Reporting Name

Sequential Maternal Screen, Part 1

Useful For

Prenatal screening for Down syndrome and trisomy 18


Prenatal screening for neural tube defects (this is only applicable to Part 2 [second trimester] of the test)

Testing Algorithm

Sequential maternal screening is a 2-part test, with first- and second-trimester components. It requires a nuchal translucency (NT) measurement and blood draw in the first trimester. If the result from Part 1 indicates a risk for Down syndrome that is higher than the screen cutoff, the screen is completed and a report is issued. If Part 1 results are negative, an additional blood draw in the second trimester is required (see SEQF / Sequential Maternal Screening, Part 2, Serum). If the second specimen is not received for sequential screening, the results are uninterpretable and no maternal risk will be provided.


The following are available in Special Instructions:

-Sequential Maternal Serum Screening Testing Process

-Prenatal Aneuploidy Screening and Diagnostic Testing Options Algorithm

Method Name

Two-Site Immunoenzymatic (Sandwich) Assay

Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type


Specimen Required

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 Medical 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 form in Special Instructions.


When Part 1 is negative, Part 2 must be completed in order to receive an interpretable result. If collecting a second-trimester specimen is expected to be difficult, order first-trimester screening instead (see 1STT / First Trimester Maternal Screen).


The ultrasound and blood draw must be completed within a gestational window of 10 weeks, 0 days and 13 weeks, 6 days, which corresponds to a crown-rump length (CRL) range of 31 to 80 mm.



Preferred: Red top

Acceptable: Serum gel

Specimen Volume: 1 mL

Collection Instructions: Immediately spin down.

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 7 days
  Frozen  90 days

Reject Due To


Mild OK; Gross reject


Mild OK; Gross OK





Reference Values

An interpretive report will be provided. See Interpretation section for more details.

Day(s) and Time(s) Performed

Monday through Friday; 8 a.m.-4:30 p.m.

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 U.S. Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
SEQU Sequential Maternal Screen, Part 1 In Process


Result ID Test Result Name Result LOINC Value
29451 Recalculated Maternal Serum Screen 43995-0
29452 Collection Date 1 33882-2
29453 Maternal Birthdate 21112-8
29890 Calculated Age at EDD 43993-5
29454 Maternal Weight 3141-9
29455 Maternal Weight 29463-7
DIAB1 Insulin Dependent Diabetes 33248-6
RACE_ Black Race 32624-9
IVF1 IVF 47224-1
SNDT1 Scan Date 34970-4
FET1 Number of Fetuses 11878-6
CRL1A CRL Measure 1 11957-8
CRL2A CRL Measure 2 11957-8
CHOR1 Chorions In Process
29891 GA on Collection by U/S Scan 11888-5
NT1 NT 33069-6
NTTB1 NT Twin B 33069-6
29468 PAPP-A 32123-2
29469 Down Syndrome Screen Risk Estimate 43995-0
29470 Down Syndrome Maternal Age Risk 49090-4
29471 Trisomy 18 Screen Risk Estimate 43994-3
29472 Interpretation 49586-1
29473 Additional Comments 48767-8
29474 Recommended Follow Up 80615-8
29487 General Test Information 62364-5
32344 Other Information 48767-8