Completing the Multiple Marker Screening requisition
This guide is for sonographers completing the ultrasound information section of the Multiple Marker Screening (MMS) requisition, when a prenatal screening test incorporating a nuchal translucency (NT) measurement is requested.
A PDF version of the guide is available for you to print and keep on hand:
Which screening tests incorporate NT measurement?
- Enhanced First Trimester Screening (eFTS) for singletons.
- Nuchal Translucency + Second Trimester Screening (NT+STS) for vanishing twin/co-twin demise pregnancies.
Having your own Ontario NT ID number is required
You must have an Ontario NT ID number to be authorized to perform NT ultrasounds for MMS without supervision. The Ontario MMS labs will not process the screen without the NT ID number, name, and signature of an Ontario NT-certified ultrasound practitioner.
Protect the accuracy of screening by not sharing your Ontario NT ID number with others.
Obtaining an NT measurement
Use the CRL cut-off (between 45 mm and 84 mm) when determining if a pregnant individual is eligible for eFTS or NT + STS. Do not use gestational age cut-offs.
An NT measurement cannot be obtained: what is next
If you cannot obtain an NT measurement and:
| the CRL is <45 mm |
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Rebook the patient according to the guidelines of your place of practice. |
| the CRL is 45-84mm (correct time window for NT) |
|
| the CRL is ≥84mm: |
|
An NT measurement is obtained: what is next
- Take note of whether the NT measurement is increased (3.5 mm or higher) as that guides the ultrasound reporting. An increased NT measurement is associated with a higher chance for fetal loss and conditions that include chromosome differences (e.g. trisomy 21 and trisomy 18), single gene disorders (e.g. Noonan syndrome), and structural differences (e.g. cardiac defects or diaphragmatic hernia).
- Regardless of NT measurement, complete the Ultrasound (U/S) Information section on the MMS requisition.
NT ultrasound following Non-Invasive Prenatal Testing (NIPT)
A pregnant individual who has undergone NIPT may not present with an MMS requisition at the time of their NT ultrasound, and there is no need to follow up with their health-care practitioner for one.
If NIPT is initiated as a primary screening test, a stand-alone 11-14 week (NT) ultrasound is recommended. Other screening tests (e.g. eFTS) are not generally recommended given that NIPT is more accurate.
Instructions for completing the requisition
Below are the steps required to complete the Ultrasound (U/S) Information section on the MMS requisition in various scenarios for singleton and twin pregnancies. Providing incorrect or missing information can delay the patient's risk assessment or affect the accuracy of the calculation.
Once the requisition is completed, scan a copy into the patient file for your records. This provides back up should the requisition be misplaced.
Singleton Pregnancies
The pregnant individual is to proceed with the blood draw, which is usually on the same day of the NT ultrasound but this is not required. The blood draw can be done anytime after the NT ultrasound as long as the pregnant individual is within the eFTS window based on CRL measurements.
| Accessible version of above visual (text only) |
Visual represents a screen shot of the Ultrasound (U/S) Information section with the following instructions:
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Singleton pregnancies with vanishing twin/co-twin demise
Pregnancies with a suspected or confirmed vanishing twin/co-twin demise can have an NT measurement, followed by Second Trimester Screening (14w0d to 20w6d). The Second Trimester Screening blood draw can be done 8 weeks after demise. Enhanced First Trimester Screening (eFTS) is not recommended for these pregnancies.
Scenario 1: patient appropriately presents with an MMS requisition for NT + Second Trimester Screening (NT + STS)
You can complete the MMS requisition as indicated above for the viable fetus. The pregnant individual is then to proceed with the STS blood draw after the date indicated by their ordering health-care practitioner within the "test requested" section. Please instruct pregnant individual to contact their health-care practitioner if they are unsure of when to go for the blood draw. You are not required to provide this information.
Scenario 2: patient presents with an MMS requisition for eFTS, but a suspected or confirmed vanishing twin/co-twin demise is identified at the time of the NT ultrasound
Although the patient cannot have eFTS based on the finding of vanishing twin, we still recommend completing the MMS requisition if it was provided by the ordering practitioner, and instructing the patient to go for the blood draw. We do not recommend relaying to the patient that eFTS cannot be done. This is because providing advice regarding prenatal genetic screening is outside of sonographers' scope of practice. Upon receipt of the blood sample, the MMS lab will notify the ordering practitioner of the next steps, which would usually be to arrange an STS blood draw between 13w0d-20w6, and 8 weeks after the estimated date of demise.
These are the guidelines for completing the form in this scenario:
| Accessible version of above visual (text only) |
Visual represents a screen shot of the Ultrasound (U/S) Information section with the following instructions:
|
Twin pregnancies
Non-Invasive Prenatal Testing (NIPT) is now funded by the Ministry of Health (MOH) for all twin pregnancies. Concurrently, First Trimester Screening (FTS) for twin pregnancies has been discontinued in Ontario. A stand-alone nuchal translucency (NT) ultrasound is still recommended for twin pregnancies, where available.
If a twin pregnancy was identified prior to the NT ultrasound and the pregnant individual appropriately does not present with an MMS requisition, you can proceed with the stand-alone NT ultrasound, and do not need to record the NT measurement on the requisition or send the patient for FTS blood draw.
What if an individual pregnant with twins still presents with the MMS requisition?
Even though FTS has been discontinued for twin pregnancies, there might be times when the pregnant individual still presents with the MMS requisition. This could be because the twin pregnancy is only identified at the time of the NT ultrasound or their health-care practitioner isnot aware that FTS has been discontinued for twin pregnancies.
Although the patient cannot have FTS, we still recommend completing the MMS requisition if it was provided by the ordering practitioner, and instructing the patient to go for the blood draw. We do not recommend relaying to the patient that FTS is in fact not needed. This is because providing advice regarding prenatal genetic screening is outside of sonographers' scope of practice. Upon receipt of the blood sample, the MMS lab will notify the ordering practitioner that FTS for twins has been discontinued and OHIP-funded NIPT is available.
These are the guidelines for filling out the form in this scenario:
| Accessible version of above visual (text only) |
Visual represents a screen shot of the Ultrasound (U/S) Information section with the following instructions:
|
Frequently Asked Questions
| Can I tell the patient that they do not need enhanced First Trimester Screening(eFTS) if they had Non-Invasive Prenatal Testing (NIPT)? |
| Although eFTS is generally not warranted after a low risk NIPT result, we do not recommend relaying this information to your patients presenting with a Multiple Marker Screening requisition. There may be some circumstances when health-care practitioners use their clinical judgement to intentionally order eFTS even if the patient had NIPT. More generally, providing advice regarding prenatal genetic screening is outside the sonographers' scope of practice. |
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