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. 2017 Nov 10;2017(11):CD011767. doi: 10.1002/14651858.CD011767.pub2

3. Traditional screening tests (mostly for T21)a.

Screening tests First trimester
(before 14 weeks’ gestation) 		Second trimester
(14 to 20 weeks’ gestation)
Ultrasonography

  • NT measurement

  • Various morphologic measurements that modify the prior risk established
Combined test

  • hCG (free β or total)

  • PAPP‐A

  • NT measurement

 NA
Triple test NA

  • hCG (free β or total)

  • uE3

  • AFP
Quadruple test NA

  • hCG (free β or total)

  • uE3

  • AFP

  • inhibin A
Sequential testb

  • free β hCG

  • PAPP‐A

  • NT measurement

  • Invasive test is offered if 1st trimester result is positive

  • Quadruple test is offered if 1st trimester result is negative
Contingent testb

  • free β hCG

  • PAPP‐A

  • NT measurement

  • Invasive test is offered if 1st trimester result is positive

  • Quadruple test is offered after an intermediate 1st trimester result

  • No test is offered after a low‐risk result
Serum integrated testc

  • PAPP‐A

  • Triple or Quadruple test
Integrated testc

  • PAPP‐A

  • NT measurement

  • Quadruple test

Maternal age is often included in the algorithm for prenatal screening tests. AFP: alpha‐fetoprotein, hCG: human chorionic gonadotropin, NA: not applicable, NT: nuchal translucency, PAPP‐A: pregnancy associated plasma protein A and uE3: unconjugated estriol.

a(Gekas 2009; Okun 2008; Wald 2005).
 bA test result was available after first‐trimester screening test.
 cSingle test result available after second‐trimester screening test.