What's Next? Follow-up of Screen Positive MMS Results for Trisomy 21

In FY 2020-2021, 6.8% of pregnancies that had MMS (eFTS, MSS and other) had a screen positive result for trisomy 21 (Down syndrome) or trisomy 18 (Edwards syndrome). A "screen positive" result means there that there is a higher chance for the pregnancy to have trisomy 21 or trisomy 18, but it does not mean that the pregnancy definitely has one of these chromosome differences. Most of the time when there is a screen positive result, the pregnancy does not have trisomy 21 (PPV 2-4% depending on MMS modality) or trisomy 18 (PPV 6-20% depending on MMS modality). However, pregnant individuals with a screen positive MMS result may feel anxious and have lots of questions about what the result means and the next steps. Continue reading to learn more about the next steps after a screen positive MMS result and what pregnant individuals chose to do in FY 2020-2021.

Claire's Story

Meet Claire. Claire is a 25 year old individual at EDD with a singleton pregnancy. Following a discussion with her health-care practitioner about the option of prenatal screening, as well as reviewing if prenatal screening was right for them, Claire opted to have Enhanced First Trimester Screening (eFTS). Claire's health-care practitioner reviewed how to get eFTS with her.

Approximately 4 days after Claire's blood collection for eFTS, her health-care practitioner received the result; it was screen positive for trisomy 21 with a chance of 1 in 110 (or 0.9%). After reviewing the clinical information on the report for accuracy, the health-care practitioner informed Claire of the result, reviewed what a screen positive MMS result meant, and discussed the next steps, including the options of publicly-funded NIPT, diagnostic testing (chorionic villus sampling (CVS) or amniocentesis depending on gestational age), or no further follow-up with continuation of routine obstetrical care. The health-care practitioner used information on the PSO website to guide them in this discussion.

In FY 2020-2021, there were 6,234 pregnancies like Claire's with a screen positive eFTS result for trisomy 21, representing a screen positive rate of 6.8%.

What follow-up did pregnant individuals with a screen positive MMS result for trisomy 21 opt to have?

Pregnant individuals with a screen positive MMS result will often ask, "what should I do next?" While the majority of pregnant individuals with a screen positive MMS result for trisomy 21 in FY 2020-2021 opted to have publicly-funded NIPT, some will opt to have diagnostic testing or no further screening or testing. Decisions may be influenced by many factors such as personal test results, gestational age, and personal values and beliefs.

Check out PSO's website for more information on Results and Next Steps.

Data notes:

BORN Ontario, 2020-2021

MMS screen and screen positive rate for T21 and T18 for all labs combined, for singleton pregnancies among Ontario residents, stratified by modality.

Number of singleton pregnancies among Ontario residents who follow up in various ways after receiving a screen positive result for T21 on MMS.

1. Data were extracted from the BORN Information System (BIS) on 4 Oct, 2023. Note that data submission to the BIS is both voluntary and open to updates and amendments. This table represents a snapshot of the BIS on the date of data extraction.

2. Fiscal year was defined by estimated date of delivery. Each fiscal year ranges from April 1 to March 31, inclusive.

3. The cohort timeline was defined by pregnant person estimated date of delivery.

4. Only singleton pregnancies were included in this analysis.

5. Only Ontario residents were included in this analysis.

6. BORN Ontario strives to better understand how our data can be used to inform health system partners on the intersection between social determinants of health, indigeneity, and perinatal and child health outcomes. This table includes data that may or may not support reflections on indigeneity and health equity. We cannot conclusively or accurately identify the extent to which BORN data reflect indigeneity and equity-deserving groups. This pursuit is ongoing, and we appreciate your support and ideas related to enabling our efforts in pursuit of more equitable outcomes and programming.

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