Down's syndrome: antenatal testing Flashcards
Down’s syndrome: antenatal testing
NICE issued updated guidelines on antenatal care in 2021 including advice on screening for Down’s syndrome
-Combined test is now standard - 11-13+6w
–done between 11 - 13+6 weeks
–nuchal translucency measurement + serum B-HCG + pregnancy-associated plasma protein A (PAPP-A)
–Down’s syndrome is suggested by ↑ HCG, ↓ PAPP-A, thickened nuchal translucency
–trisomy 18 (Edward syndrome) and 13 (Patau syndrome) give similar results but the hCG tends to lower
-Quadruple test - 15-20w
–if women book later in pregnancy the quadruple test should be offered between 15 - 20 weeks
–quadruple test: alpha-fetoprotein, unconjugated oestriol, human chorionic gonadotrophin and inhibin A
Results of combined or quadruple tests
Both the combined and quadruple tests return either a ‘lower chance’ or ‘higher chance’ result
‘lower chance’: 1 in 150 chance or more e.g. 1 in 300
‘higher chance’: 1 in 150 chance or less e.g. 1 in 100
Non-invasive prenatal screening test (NIPT)
-‘higher chance’ results she will be offered a second screening test
–(NIPT) or a diagnostic test (e.g. amniocentesis or chorionic villus sampling (CVS).
Given the non-invasive nature of NIPT and extremely high sensitivity and specificity, it is likely this will be the preferred choice for the vast majority of women.
