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Screen positive results

A screen positive result means the chance the baby has Down syndrome, trisomy 18, or an open neural tube defect is above the cut-off.  (The cut-off differs for each of the conditions and screening tests.)
  • A screen positive test does not mean that the baby has the condition for which they screened positive
  • If a result is screen positive, the patient should be offered further counselling and testing to determine if the baby is affected by the condition for which they screened positive.
  • The chance the baby is affected by the condition for which they screened positive is the risk printed on the result.
Following a screen positive result, the recommended follow up varies depending upon which screen the patient had.

Screen positive for:

What is offered

Timing

ONTD
– Referral to Genetics
– Ultrasound
– Amniocentesis
– Any time
– 15-20 weeks
– 15-22 weeks
Trisomy 18
– Referral to Genetics
– Ultrasound
– Amniocentesis
– Any time
– 15-20 weeks
– 15-22 weeks
Down syndrome
– Referral to Genetics
– CVS*
– Ultrasound
– Amniocentesis
– Any time
– 11-13 weeks
– 15-20 weeks
– 15-22 weeks
* CVS (chorionic villus sampling) would be available to women who screen positive for a chromosome problem in the first trimester (First Trimester Combined Screening)
The type of screen a patient may have and the follow up recommended by screen and screen positive result are listed below:
1)  Integrated Prenatal Screening (IPS) and Serum Integrated Prenatal Screening (SIPS):
Step 1. First trimester 11 – 13+6/7 weeks
  • IPS: NT measuremnt then maternal serum: PAPP-A
  • SIPS: maternal serum: PAPP-A
Step 2. Second trimester: 15 – 20+6/7 weeks
  • IPS: maternal serum: AFP, uE3, hCG
  • SIPS: maternal serum: AFP, uE3, hCG, DIA
IF screen positive discuss options and offer a referral to genetic services.
a)  Screen positive for chromosome problem – offer amniocentesis between 15-22 weeks
i)  Abnormal results – discuss options
ii) Normal results – most results will be normal
b)  Screen positive for open neural tube defects – offer ultrasound between 15-20 weeks and/or amniocentesis
i)  Abnormal results – discuss options
ii) Normal results – most results will be normal; with a high MS-AFP there is a risk of pregnancy complications
2)  First Trimester Combined Screening (FTS):
First trimester 11 – 13+6/7 weeks
  • NT measuremnt then maternal serum: PAPP-A, ƒbhCG
IF screen positive discuss options and offer a referral to genetic services.
a)  Offer chorionic villus sampling (CVS) between 11-13 weeks
i)  Abnormal results – discuss options
ii) Normal results – most results will be normal; continue with open neural tube defect screening with MS-AFP performed between 15-20 weeks and an ultrasound between 18-20 weeks
b)  Offer amniocentesis between 15-22 weeks
i)  Abnormal results – discuss options
ii) Normal results – most results will be normal; continue with open neural tube defect screening with MS-AFP performed between 15-20 weeks and an ultrasound between 18-20 weeks
3)  Maternal Serum Triple and Quadruple Screening:
Second trimester: 15 – 20+6/7 weeks
  • Triple screening: maternal serum: AFP, uE3, hCG
  • Quadruple screening: maternal serum: AFP, uE3, hCG, DIA
IF screen positive discuss options and offer a referral to genetic services.
a)  Screen positive for chromosome problem – offer amniocentesis between 15-22 weeks
i)  Abnormal results – discuss options
ii) Normal results – most results will be normal
b)  Screen positive for open neural tube defects – offer ultrasound between 15-20 weeks and/or amniocentesis
i)  Abnormal results – discuss options
ii) Normal results – most results will be normal; with a high MS-AFP there is a risk of  pregnancy complications