First trimester fetal anomaly screening: trisomy 18 and trisomy 13

First trimester screening procedures for trisomy 18 (T18) and trisomy 13 (T13), also known as Edwards' syndrome and Patau's syndrome.

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First trimester screening for T18 and T13

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This document explains the combined screening test for trisomy 18 and trisomy 13. It outlines the conditions and sets out the:

  • national standards for detection
  • risk cut off numbers
  • actions for higher risk and lower risk results

The NHS fetal anomaly screening programme (FASP) test for these conditions.

Published 1 January 2015