Maternal Serum Screening

Maternal serum screening tests help identify pregnancies at increased risk for Down syndrome, trisomy 18, or open neural tube defects such as spina bifida. These tests have traditionally been performed in the second trimester and measure the levels of specific protein markers in maternal blood. Newer tests now combine first-trimester fetal ultrasound measurements along with measurements of biochemical markers in maternal blood to predict risk. ARUP offers second-trimester as well as first-trimester, integrated, and sequential screens.

* Sonographer providing NT measurement must be certified by NTQR (SMFM) or FMF. Please contact a genetic counselor at (800) 242-2787 x2141 prior to sending first sample to ensure acceptability.

Detailed test changes effective February 20, 2018

Effective February 20, 2018 the following changes will be implemented with the new maternal serum screen tests. This is information is in addition to the quarterly hotline documents.

1. Required information can now be entered electronically through client interface instead of on the ARUP patient history form.

Click here for a list of suggested entries for required information.
Clients who wish to continue using the paper form can access the updated patient history form here.

2. Changes in risk calculation for Open Neural Tube Defects (ONTD)

Reporting of twin results has been simplified. Expected twin AFP MoMs will now be twice that expected in a singleton (median singleton MoM: 1.00; median twin MoM: 2.00)

Cutoffs will be as follows:

  • Singleton: 2.50 MoM
  • Twins: 4.50 MoM
  • Diabetic (singleton): 1.90 MoM
  • Diabetic (twins): 2.94 MoM

3. Down syndrome - smoking will now be factored into the risk calculations

4. Changes to patient report

  • Maternal race will be reported as black, nonblack, or unknown
  • Maternal weight will be reported in the units of measurement provided to ARUP (pounds or kilograms)
  • Units of measurement for PAPP-A will now be reported as ng/mL
  • PAPP-A MoMs will no longer be reported on Integrated-1 reports but will be listed as part of the Integrated-2 reports
  • Units of measurement for CRL will now be reported in millimeters (mm)
  • Interpretation verbiage and formatting will change
  • Enhanced report format and design will be updated

5. Repeat screens will only provide NTD risk

Down syndrome and trisomy 18
  • A repeat maternal serum screen will not provide Down syndrome or trisomy 18 risks if the original screen provided risks, and the original sample was drawn within the appropriate gestational age window for the test ordered.
  • Risks will be provided on repeat specimens

Please refer inquiries about these changes to an ARUP genetic counselor at 800-242-2787 x2141.

Patient Information