prenatal Diagnosis Flashcards
exam 2
probability, not a definitive answer and provides individual risk assessment
screening
definitive and procedure-related risk of pregnancy loss
diagnostic
example of screening (3)
(1) ultrasound
(2) maternal serum marker
(3) non-invasive prenatal testing (NIPT)
example of diagnostic (3)
(1) chorionic villus sampling (CVS)
(2) amniocentesis
(3) cordocentesis (PUBS)
when is nuchal translucency ultrasound performed?
at 11-13+ weeks
Nuchal translucency ultrasound measures
nuchal transulency- a fluid under the skin behind the fetal neck
a nuchal translucency measurement of >3.9 mm is
associated with an increased risk for aneuploidy and fetal heart defects
most fetuses with an increased nuchal translucency do not have
aneuploidy
nuchal trans. ultrasound detects
~60% of fetuses with aneuploidy
fetal anatomic survey can be performed
any time after 18 weeks
fetal anatomic survey can detect
structural fetal anomalies such as congenital heart defects
fetal anatomic survey can detect “soft- markers” for anueploidy such as
echogenic intracardiac foci
most structural anomalies increase
the chance for aneuploidy and/or other genetic syndromes
soft-markers
are not fetal anomalies but can be used to adjust the chance for aneuploidy in a pregnancy
In fetal anatomic survey, level II ultrasound is performed in centers with special training and equipment, and can detect:
- open neural tube defects
- congenital heart defects
- down syndrome
- trisomy 18
EIF
soft-marker
EIF increases the chance f ____ but is not a birth defect
T21
maternal serum marker screening is offered
to all pregnant women to measure proteins and hormones produced by the fetus and placenta
maternal serum marker screening can evaluate the
chances for Down syndrome, trisomy 18, and open neural tube defects
maternal serum marker screening: results are presented as
1/### fraction and it is known at the positive predictive value
chance that a positive result is a true positive
positive predictive value
positive predictive value depends on the
condition, sensitivity, specificity a prior risk for the condition
screen separates women into _____________ groups based on whether the risk is above or below the laboratory-determined cut off for screen positive or screen negative
high or low risk
most women with “ high risk” results will have an
unaffected fetus
maternal serum marker screening:
first trimester screen (11-13+weeks)
- nuchal translucency
- serum analytes: free Beta-hcG, PAPP-A
maternal serum marker screening:
second trimester Quad (15-21+ weeks)
-serum analytes: AFP, uE3, hCG, Inhibin A
combine information from first and second trimester
integrated and sequential screens
integrated and sequential screens pros
slightly increased detection rates and/or decreased false positive rates (FPR)
maternal serum marker screening:
down syndrome
- first trimester: 82-87%
- Quad screen: ~80%
- Integrated/sequential: ~95-96%
maternal serum marker screening:
Trisomy 18
- first trimester: 80%
- Quad screen: ~80%
- Integrated/sequential: ~80%
maternal serum marker screening:
ONTD
- first trimester: -
- Quad screen: ~80%
- Integrated/sequential: ~80%
maternal serum marker screening:
FPR
- first trimester: 5%
- Quad screen: 5%
- Integrated/sequential: ~5%
who is indicated for additional testing?
- routine for all
- more advanced testing depends on advanced maternal age, past history
non-invasive prenatal testing via cell-free DNA testing
evaluation of cell-free DNA in maternal serum
non-invasive prenatal testing via cell-free DNA testing is offered to
women at increased risk for aneuploidy
non-invasive prenatal testing via cell-free DNA testing when can it be preformed?
any time 10 weeks to delivery
cell-free DNA in Maternal plasma, 10% of the DNA fragments in a pregnant woman’s blood are from the
placenta
non-invasive prenatal testing via cell-free DNA testing can evaluate the chances for
trisomies 21, 18, 13, monosomy X in the fetus/placenta
non-invasive prenatal testing via cell-free DNA testing vs maternal serum marker screening
significantly higher detection rates and lower false positive rates
positive predictive values are generally higher in
traditional maternal serum marker screening
NIPT performance on trisomy 13
80% sensitivity vs >99% specificity
positive predictive trend in age
increases as we grow older
Chorionic villus sampling (CVS) is preformed at
10-13+ weeks
Chorionic villus sampling (CVS) risk
1/300-1/500 for miscarriage
Chorionic villus sampling (CVS) cannot test for
neural tube defects
Amniocentesis is preformed at
15+ weeks
amniocentesis risk
1/300-1/500 for miscarriage
amniocentesis detects
98% of open neural tube defects
alpha-fetoprotein
neural tube defect
pre-implantation genetic testing can be
pre-screened because they grow in a multi-cell state
pre-implantation genetic testing
typically uses microarray-based testing to screen for aneuploidy in embryos
aneuploidy
extremely common in embryos
pre-implantation diagnosis
typically uses a family-specific test to screen for a single gene disorder in embryos
abnormal number of chromosomes in the cell
aneuploidy
