Prenatal Testing Flashcards
What is measured in FTS?
- NT measurement
2. PAPP-A and beta hCG
What conditions does FTS assess risk for?
T21 and T18
When is FTS most accurate?
11-12 weeks, but usually performed anytime between 10w3d and 13w6d
Tell me about PAPP-A: what is it produced by? When is it helpful to measure? Levels in T21 pregnancies? Levels in T18 pregnancies?
placenta, helpful only in the 1st trimester, significantly decreased in T21, less dramatically decreased in T18
Tell me about hCG: What is is produced by? Levels in T21 pregnancies? Levels in T18 pregnancies? Pattern over time?
placenta, nearly doubled in T21, markedly decreased in T18, levels peak at 8 weeks and decrease steadily to 20 weeks when they plateau
Analyte patterns in FTS for T21 and T18
T21: low papp-a, high hCG
T18: low papp-a, low hCG
Detection rate of FTS for T21 and T18
~83% for T21
~90% for T18
(%5 false positive rate)
Differential diagnoses for increased NT
- Aneuploidy (T21, Turner, etc.)
- Structural heart defect
- Genetic syndromes (i.e. Noonan)
- Adverse outcome
What is measured in 2nd tri MSS?
- AFP
- hCG
- uE3
- Inhibin-A
When is 2nd tri MSS performed?
14-22 weeks, most accurate 15-18 weeks
What does 2nd tri MSS provide rise assessment for?
ONTDs, T21, T18
What is the detection rate of 2nd tri MSS?
~80% for all conditions (with 5% FPR)
Tell me about AFP: where is it produced? What is the detection rate for spina bifida? What is the detection rate for anencephaly? Pattern over time?
synthesized in the liver and excreted by the kidneys, detects ~80% of spina bifida, detects ~95% of anencephaly, increases steadily throughout pregnancy
Tell me about uE3: what is it produced by? what pathway is it involved in? pattern over time?
placenta, cholesterol pathway, increases steadily throughout pregnancy
Tell me about inhibin A: what is it produced by? pattern over time?
mostly by the placenta, remains constant from 10-25 weeks
What factors are included in the algorithm for calculating a quad screen?
maternal age, weight, diabetes, race, number of fetuses, GA, previous child with T21
Analyte patterns in quad screen for T21 and T18
T21: low AFP, high hCG, low uE3, high inhibin A
T18: All low
Does FTS or quad screen have a higher detection rate for T21 and T18?
FTS (80-90%)
quad screen is only 70-80%
MSS results indicating fetal demise
low hCG, low uE3, high AFP if recent but low AFP if not
MSS results indicating triploidy
high AFP, high uE3, high hCG if diandry but low if digyny
Conditions indicated by very low uE3 (2)
SLO and x-linked ichthyosis
MSS results congenital finnish nephrosis
extremely high AFP (levels of 30+)
Integrated screening steps and detection rate
1st trimester screening (NT, PAPP-A, hCG) –> 2nd trimester screening (AFP, uE3, inhibin A)
- 91-96% detection rate for T21 and T18
- results are withheld until both are complete
- eliminates option of CVS
Indications for NIPT
AMA, abnormal serum screening, personal or fam hx of aneuploidy, abnormal ultrasound
types of Herpes
- type 1 & type 2
- type 2 is genital form, which causes the problem
Time of Herpes greatest risk
- primary maternal infection causes the greatest risk early in pregnancy and near term
- 1st trimester infection poses risk for CNS malformations
- no curable treatment
High AFP differentials
- ONTDs
- abdominal wall defects
- finnish nephrosis (really high)
- adverse outcomes (
