Condition	HCG	PAPP-A	AFP	Inhibin A	Nuchal translucency
Trisomy 21	↑	↓	↓	↑	↑
Trisomy 18	↓	↓	↓	normal	↑↑
Trisomy 13	↓	↓	normal	normal	↑

Mnemonic

• Trisomy 21 (Down syndrome)
  • Drinking age (21).
  • Markers for Down syndrome are hi up: ↑ hCG, ↑ inhibin.
• Trisomy 18 (Edwards syndrome)
  • Election age (18).
  • In Edwards syndrome, every prenatal screening marker decreases.
• Trisomy 13 (Patau syndrome)
  • Puberty at age 13.

Down syndrome

Edwards syndrome

• Rocker-bottom feet can also be found in Patau syndrome.
  • This is a rocking chair

Patau syndrome

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• Aplasia cutis congenita: congenital absence of skin; most commonly scalp lesions with a punched-out appearance that may extend to the bone or the dura