Down鈥檚 syndrome, Edwards鈥� syndrome and Patau鈥檚 syndrome screening pathway
Updated 30 January 2025
Applies to England
漏 Crown copyright 2025
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This flowchart (text description and illustration below) describes the screening pathway for Down鈥檚 syndrome, Edwards鈥� syndrome and Patau鈥檚 syndrome including non-invasive prenatal testing (NIPT).
1. Offer information and screening for T21, T18 and T13
Offer the pregnant woman screening for Down鈥檚 syndrome (trisomy 21), Edwards鈥� syndrome (trisomy 18) and Patau鈥檚 syndrome (trisomy 13) and information about the screening test(s).
Before screening is carried out, the baby鈥檚 crown rump length (CRL) is measured at the .
2. Does the woman accept screening?
Yes: The woman accepts screening for:
- Down鈥檚 syndrome, Edwards鈥� syndrome and Patau鈥檚 syndrome
- Edwards鈥� syndrome and Patau鈥檚 syndrome
- Downs鈥� syndrome only
Go to question 3.
No: Offer 20-week screening scan. End of pathway.
3. Is the baby鈥檚 CRL less than 45.0mm?
Yes: Recall the woman for a repeat scan when CRL measures 45.0mm or more. Then go to question 4.
No: Go to question 4.
4. Is the baby鈥檚 CRL between 45.0mm and 84.0mm?
Yes: Carry out combined screening test for chosen conditions. Go to question 7.
No: Go to question 5.
Please note: if it is not possible to measure the baby鈥檚 nuchal translucency (NT) despite 2 attempts (鈥榯wice on the couch鈥�), further attempts do not need to be offered. The woman should be offered quadruple screening.
5. Is the baby鈥檚 head circumference (HC) between 101.0mm and 172.0mm
Yes: Offer T21 quadruple screening (Down鈥檚 syndrome only). Go to question 6.
No: Offer 20-week screening scan. End of pathway.
6. Does the woman accept quadruple screening?
Yes: Carry out quadruple test. Go to question 7.
No: Offer 20-week screening scan. End of pathway.
7. Is the result lower chance?
Yes: Offer 20-week screening scan. End of pathway.
No: Refer for discussion of further choices. Go to question 8.
8. Does the woman want further tests?
Yes: Go to question 9.
No: Offer 20-week screening scan. End of pathway.
9. Which test does the woman want?
NIPT: Carry out NIPT. Go to question 10.
CVS or amniocentesis: Carry out CVS or amniocentesis test. Go to question 12.
10. What is the result of NIPT?
Lower chance result: Offer 20-week screening scan. End of pathway.
Higher chance result: Discuss options. Go to question 11.
11. Does the woman want further tests?
Yes: Carry out CVS or amniocentesis test. Go to question 12.
No: Offer 20-week screening scan and follow-up support. End of pathway.
12. Does baby have Down鈥檚 syndrome, Edwards鈥� syndrome or Patau鈥檚 syndrome?
Yes: Discuss options with the woman. Go to question 13.
No: Offer 20-week screening scan. End of pathway.
13. What is the woman鈥檚 choice?
Continue pregnancy: Offer 20-week screening scan and follow-up support. End of pathway.
Terminate pregnancy: Offer follow-up support.