Chapter 55 Prenatal Diagnosis Of Congenital Anomalies Flashcards
There are two categories of genetic testing they can be either ____ or ______
Invasive or noninvasive
Ultrasound guided biopsy of the placenta or chorion frondosum
Chorionic Villus Sampling (cvs)
Chorionic villus sampling(cvs) tests are performed ___
10-14 weeks
Results from the chorionic villus sampling(cvs) are available within ____
1 week
In the chorionic villus sampling(cvs) how are chromosomal abnormalities detected?
By growing and analyzing the sampled villi
chorionic villus sampling; association with limb reduction defect when procedure is performed ____
Before 8 weeks
The risk of fetal loss with chorionic villus sampling(CVS) is
About 1%
Invasive procedure that allows analysis of fetal chromosomes from fetal cells in amniotic fluid
Amniocentesis
Amniocentesis results are available in
1-3 weeks
The risk for having a child with a chromosomal defect is greater in women _____
Of advanced maternal age (ama)
For genetic reasons an amniocentesis is ideally performed between
15-20 weeks
Amniocentesis may be done as early as ________ but this may lead to the development of fetal scoliosis or club foot due to _______
12 weeks
Due to reduced amount of amniotic fluid
Always obtain ______ after amnio is complete
Fetal heart rate
Optimal collection site for amniotic fluid
Away from the fetus
away from the central position portion of the placenta
away from the umbilical cord
near the maternal midline to avoid maternal uterine vessels
When performing an amniocentesis for multiple gestational pregnancies the first sac will be punctured and then what is injected into the first sack?
Indigo carmine dye
The use of ______ has also been reported in amniocentesis with multiple gestations(dye)
Methylene-blue and sterile air
Fetal blood is obtained through needle aspiration of the umbilical cord
Cordocentesis
Karyotype results from a cordocentesis are processed within ____
2-3 days
The fastest invasive procedure for genetic testing
Cordocentesis
Amniocentesis rapid results can be available within 24 hours, but only limited results are available (13, 18, 21, X/Y)
What are cordocentesisis typically used for?
Guidance for transfusions to treat fetal isoimmunization
Major protein in fetal serum
AFP
AFP is produced by what in early gestation?
yolk sac
AFP is produced by what in later gestation
fetal liver
AFP may be measured in _____ or from _______
maternal serum(MSAFP) or amniotic fluid(AFAFP)
common reason for elevated AFP
neural tube defects, anencephaly, open spina bifida
Why are neural tube defects common reasons for elevated AFP?
AFP leaks from the defect to enter the amniotic fluid and diffuses into maternal blood stream
elevation of AFP is based on levels:
greater than/equal to 2-2.5 multiples of the median(MOM)
MSAFP levels peak at
15-18 weeks gestation
2 common abdominal wall defects produce elevated AFP:
omphalocele and gastroschisis
Omphalocele: AFP leaks through the membrane that is encasing the herniated bowel or liver: ____ defect
closed defect
Gastrochisis: AFP diffuses directly into the serum and amniotic fluid from herniated bowel, lacks covering membrane: ____ defect
open defect
A fetus with a _____ lesion may produce increased levels of AFP
kidney lesion
polycystic kidneys and UT obstruction may lead to significantly higher levels of AFP because:
abnormal filtration of AFP, kidney maldevelopment and UT leakage.
frequent cause of high MSAFP levels ____
fetal death
When the AFP is elevated (greater than 3 MOM) & the cranium and spine appear normal, the risk of the fetus having a spinal defect is:
cut in half
low levels of AFP are associated with
trisomy 13, 18, 21, incorrect dates, fetal death, hydatidiform moles
quad screen includes:
AFP, hCG, Unconjugated estriol, inhibin-A
improves the sensitivity in detecting down syndrome ____(lab value)
inhibin-A
Lab values for trisomy 21
high hCG, low/decreased AFP & estriol levels
Trisomy 18 lab values
decreased hCP, AFP, & Estriol
PAPP-A levels are decreased in pregnancies affected by _____
aneuploidy
glycoprotein derived from trophoblastic tissue that is diffused into maternal circulation:
PAPP-A
glycoprotein derived from the placenta:
hCG
Normal karyotype consists of ____ chromosomes
46
abnormality in number of chromosomes:
Aneuploidy
cause of trisomy is usually:
failure of normal chromosomal division at meiosis
condition caused by a single defective gene
autosomal dominant
caused by a pair of defective genes
autosomal recessive
disorders inherited by boys from their mothers:
X-linked disorders
example of an X-linked condition in male fetuses:
aqueductal stenosis
occurrence of gene mutation or chromosomal abnormality in portion of an individual’s cells
mosaicism
NT is performed:
between 11-14 weeks gestation
One of the most common chromosomal disorders
trisomy 21
trisomy 21 is also known as
down syndrome
trisomy 21 features:
duodenal atresia(double bubble sign), brachycephaly, flattened nasal ridge, hypertelorism(increased space between eyes), cystic hygroma(enlarged space behind neck), sandal gap foot, hypoplasia or absence of the middle phalanx of the 5th digit, clinodactyly(curving of 5th finger inward)
trisomy 18 is also known as
Edwards syndrome
2nd most common chromosomal abnormality
trisomy 18
trisomy 18 features:
microcephaly(small head), choroid plexus cysts, clenched hands, rocker-bottom feet, cleft lip/palate, clubfoot
trisomy 18: _____% of infants die within the first year of life
90%
Trisomy 13 is also known as
Patau syndrome
chromosomal abnormality that mainly involves the brain
trisomy 13
trisomy 13 features:
holoprosencephaly, rocker-bottom feet, polydactyl(extra digits)
trisomy 13: ___% of infants usually die within first months of life
80%
complete extra set of chromosomes:
triploidy
triploidy most often occurs as a result of:
the ova being fertilized by 2 sperm
holoprosencephaly:
hypotelorism(close eyes)
proboscis(tube-like structure in middle of face)
cyclopia
single nostril nose
triploidy is associated with (disease)
gestational trophoblastic disease/molar pregnancy, theca-lutein cyst, preeclampsia
genetic abnormality marked by absence of X or Y chromosome
Turner’s syndrome
genetic abnormality not associated with AMA
Turner’s syndrome
most common finding in Turner’s syndrome:
cystic hygroma(fluid around back of neck)
female infants who survive with Turner’s syndrome will have
immature sexual development amenorrhea short stature webbed neck abnormal elbow angle shield chest
associated with 1st trimester increased NT and tachycardia
Turner’s syndrome
most common cardiac anomaly with Turner’s syndrome
coarctation of the aorta
identification of female gender with ______ strongly suggests Turner’s syndrome
cystic hygroma