Test Catalog

Test ID: SEQA    
Sequential Maternal Screening, Part 1, Serum

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

Sequential maternal screening is a 2-step test, with first- and second-trimester components. It requires a nuchal translucency (NT) measurement and blood collection 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 the results from part 1 are negative, an additional blood collection in the second trimester is required (see SEQB / 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

Specimen Type Describes the specimen type validated for testing


Ordering Guidance

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 1STT1 / First Trimester Maternal Screen, Serum).


If a stand-alone neural tube defect risk assessment is desired, order MAFP1 / Alpha-Fetoprotein (AFP), Single Marker Screen, Maternal, Serum.

Additional Testing Requirements

Sequential maternal screening is a 2-part test that includes a first-trimester sample (SEQA / Sequential Maternal Screening, Part 1, Serum) and a second-trimester sample (SEQB / Sequential Maternal Screening, Part 2, Serum).

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 in Special Instructions. Complete the NT/CRL Data for First Trimester/Sequential Maternal Screening form in Special Instructions.

Specimen Required Defines the optimal specimen required to perform the test and the preferred volume to complete testing


Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions:

1. 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.

2. Centrifuge and aliquot serum within 2 hours of collection.

Special Instructions Library of PDFs including pertinent information and forms related to the test


First Trimester/Sequential Maternal Screening Patient Information (T593) is required; see Special Instructions.

Specimen Minimum Volume Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.5 mL

Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis Reject
Gross lipemia OK
Gross icterus OK

Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen TypeTemperatureTimeSpecial Container
SerumRefrigerated (preferred)7 days
 Frozen 90 days