Chromosomal Defects Flashcards
1
Q
Invasive testing by amniocentesis, chorionic villous sampling, or cordocentesis is associated with a risk of miscarriage of about ___%.
A
1
2
Q
U/s screening is based onthe fact that most fetuses with chromosomal abnormalities have…
A
major structural malformations or minor ‘markers’
3
Q
The risk for many of the chromosomal defects increases with…
A
age.
4
Q
Major chromosomal defects are associated with…
A
- multiple antomic abnormalites
- mental limitations
- high mortality rate
5
Q
Genetic disease may be the result of…
A
- abnormal # of chormosomes
- abnormal structure of chromosomes
- single gene defect (dominant or recessive)
6
Q
The probablity of passing on a dominant genetic trait to your offspring is…
A
50%
7
Q
The probablity of passing on a recessive genetic trait to your offspring is…
A
25%
8
Q
This is the complete set of chromosomes in a cell, often arranged in pairs for analysis.
A
karyotype
9
Q
This is a normal balanced set of chromosomes.
A
euploid
10
Q
This is an unbalanced set of chromosomes.
A
aneuploid
11
Q
This is the presence of an extra chromosome.
A
trisomy
12
Q
This is the entire physical and physiologic makeup of an individual determined both geneticlly & environmentally.
A
phenotype
13
Q
This is the genetic composition of an individual.
A
genotype
14
Q
What increases the risk of trisomy?
A
- older mother
2. previous trisomy (another .75%)
15
Q
A major congenitial anomaly is found in…
A
3:100 births.
16
Q
__% births are complicated by minor birth defects.
A
10-15
17
Q
In the first trimester chromosomal abnormaliites are determined by…
A
- nuchal translucency
- free beta-hCG and PAPP-A
- CVS-Chorionic Villus Sampling
18
Q
This scan measures the fluid filled area at the back of the neck between 11.5 - 13.5 weeks.
A
nuchal translucency
19
Q
The nuchal translucency scan measures the fluid filled area at the back of the neck between __ weeks.
A
11.5 -13.5
20
Q
Low levels of beta-hCG and PAPP-A may indicate…
A
- abnormal implantation
- poor placental development
- a risk for trisomy 18
21
Q
The blood test and the nuchal translucency together can detect about ___ of fetuses with Downs and Edwards.
A
85%
22
Q
When abnormal blood tests and translucencies are obtained, patient’s are offered…
A
a CVS to determine chromosomal defects.
23
Q
T/F? Neural tube defects can be diagnosed with CVS.
A
FALSE, cannot
24
Q
A CVS is performed between ___ weeks.
A
9-12
25
Results from CVS are usually back in ___ days.
2-3
26
In the 2nd and 3rd trimester, chromosomal abnormalities are determined by...
1. multiple marker screening
| 2. amniocentesis
27
These biochemical screening tests have been developed to find fetal anomalies.
multiple marker screening
28
This test screens for a protein normally produced by the fetal liver.
MS-AFP
29
This test screens for a hormone produced within the placenta.
hCG
30
This test screens for an estrogen produced by both the fetus and the placenta.
uE3 (unconjugated estriol)
31
What might be wrong if MS-AFP is increased?
1. wrong dates
2. multiple gestations
3. open neural tube defects
4. ventral wall defects
5. amniotic band syndrome
32
What might be wrong if MS-AFP is decreased?
1. wrong dates
2. trisomy 13. 18, or 21
3. fetal demise
33
MS-AFP is measured in...
"MOM" (multiples of the median)
34
An elevated MS-AFP =
equal to or greater than 2 MOM
35
What might be wrong if hCG is elevated?
Downs or trisomy 21
36
What might be wrong if uE3 is decreased?
Downs or trisomy 21
37
This is offered to evaluate amniotic fluid levels of AFP and for fetal karyotyping.
amniocentesis
38
What might be wrong if amnio-AFP is elevated?
occult neural tube defect
39
Amniocentesis is usually performed around...
16 weeks.
40
Results from amniocentesis are usually back within..
7-10 days.
41
Which genetic testing procedure can be performed the earliest in a pregnacy to determine chromosomal bnormalities and karyotyping?
CVS
42
Trisomy 21 (Downs) occurs in how many births?
1:800
43
___ are the major cause of infant mortality in Downs syndrome.
heart anomalies
44
Downs syndrome patients suffer from...
1. heart anomalies
2. mental limitations
3. respiratory problems
4. eye problems
5. premature aging
45
How many cases of trisomy 21 are caught by u/s exam?
3:4
46
What are the most common u/s findings indicated trisomy 21?
1. nuchal fold >6 mm at 15-21 weeks
2. cardiac defects
3. duodenal atresia
4. short femur and humerus
47
Trisomy 21 infants may present with what physical features?
1. flattened nasal bridge
2. round small ears
3. protruding tongue
4. echogenic bowel
5. sandal gap
6. clinodactyly
7. simian crease
48
What sonographic sign indicates duodenal atresia?
'double-bubble' sign
49
This is the most common trisomy.
21 or Downs
50
This is the 2nd most common trisomy.
18 or Edwards
51
Edwards is considered a lethal anomaly with __ of infants dying within the first year.
90%
52
Infants with Edwards may present with what physical features?
1. clinodactyly
2. omphalocele**
3. choroid plexus cysts
4. strawberry-shaped head
5. micronathia (weak chin)
53
This trisomy is also called Patau's Syndrome.
Trisomy 13
54
Infants with Patau's may present with what physical features?
1. holoprosencephaly*
2. polydactyly
3. cleft lip
4. proboscis
55
This chromosomal defect occurs as a result of an ova being fertilized by two sperm.
triploidy
56
Triploidy may occur in _% of conceptions and most fetuses will ___ in the first trimester.
1%, spontaneously abort
57
T/F? Triploidy is considered a lethal condition.
true
58
This syndrome is a genetic abnormality marked by the complete or partial absence of an X chromosome.
Turner's
59
The prognosis for Turner's is especially grave when the fetus presents with a large ___ and edema or hydrops.
cystic hygroma
60
How many infants with Patau's die within the first year?
85%
61
People with Turner's who survive infancy often have these anomalies...
1. immature sexual development
2. amenorrhea
3. short stature
4. webbed neck*
5. shield-shaped chest
6. normal intelligence
62
This condition of dilated lateral cerebral ventricles can be identified via prenatal u/s.
ventriculomegaly
63
Ventiriculomegaly is commonly caused by...
1. choromosomal or genetic defect
2. intrauterine hemorrhage or infection
3. who knows?
64
Ventriculomegaly is seen with what common chromosomal defects?
trisomies 21, 18, 13, & triploidy
65
A lateral ventricle with a diameter between ___ is usually considered mild or borderline ventriculomegaly.
10-15 mm
66
A lateral ventricle with a diameter of ___ is usually considered hydrocephalus.
greater than 15 mm
67
This is a structural anomaly of the brain in which the developing forebrain fails to divide into two separate hemispheres and ventricles.
holoprosencephaly (HPE)
68
HPE is most commonly seen in the chromosomal defects of ___
trisomies 13 & 18
69
The hallmark of HPE is the absence of...
cavum septum pellucida & the lack of formation of midline structures.
70
What are the three degrees of HPE?
1. alobar
2. semilobar
3. lobar
71
This is the most severe degree of HPE characterized by a monoventricular cavity and fusion of the thalami.
alobar
72
This is the more moderate degree of HPE wherein the cerebral hemispheres fused at the front only. The brain has a single horseshoe shaped central ventricle.
semilobar
73
This is the mildest degree of HPE with normal separation of ventricles and thalami but the absence of the septum pellucidum.
lobar
74
These degrees of HPE are often accompanied by microcephaly and facial abnormalities.
alobar and semilobar
75
Prenatal diagnoses of this brain abnormality is based on the identification of a disproportionately reduced head circumference.
microencephaly
76
T/F? In more than 80% of microencephaly cases, here is severe mental limitations.
FALSE, 50%
77
Choroid plexus cysts are found in about 2% of fetuses at __ weeks gestation, but in most cases they resolve by 28 weeks.
16-24 weeks
78
If choroid plexus cysts are ___, the risk of trisomy 18 is increased only marginally.
isolated
79
This condition can be suspected by the absence of the cavum eptum pellucidum and enlargement of the posterior horn of the lateral ventricle.
agenesis of the corpus callosum
80
This is the bundle of fibers that connects the two cerebral hemispheres.
corpus callosum
81
The corpus callosum develops at ___ weeks gestation.
12-18 weeks
82
T/F? In about 90% of isolated agenesis of corpus callosum cases, the development is normal.
true
83
This refers to the spectrum of abnormalities of the cerebellar vermis, cystic dilation of the 4th ventricle, and enlargement of the cisterna magna.
dandy-walker syndrome
84
The overall incidence of of chromosomal defects in Dandy-Walker Syndrome is about __%, usually trisomies ___.
40%; 18, 13 or triploidy
85
In Dandy-Walker Syndrome, an enlarged cisterna magna is diagnosed if the distance from the vermis to the inside of the skull is...
more than 10 mm.
86
T/F? In Dandy-Walker Syndrome there is a cystic dilation of the third ventricle.
FALSE, fourth
87
T/F? In about 80% of trisomy 21 cases, there is a strawberry shaped head.
FALSE, trisomy 18
88
This abnormality is a relative shortening of the occipitofrontal diameter.
brachycephaly
89
Brachycephaly is found in cases of...
Robert's and Down's
90
This facial abnormality is found in about 40% of chromosomal defects and most commonly in trisomies 13 & 18.
facial cleft
91
This facial abnormality is a moderate posterior position of the mandible.
micrognathia
92
Micrognathia is found mainly in trisomies...
18 and triploidy.
93
This facial abnormality is a common feature of trisomy 21.
macroglossia
94
This facial abnormality is defined as a nasal bone that is not visible or with a length of less than 2.5 mm.
nasal hypoplasia
95
This is a 2nd trimester marker that is the single most sensitive impact on screening for trisomy 21.
nasal hypoplasia
96
In about 85% of neonates with trisomy __, the ear length is below the 3rd percentile.
21
97
This is a developmental abnormality of the lymphatic system.
cystic hygroma
98
Cystic hygroma is almost always seen in ___ syndrome.
turners
99
Diaphragmatic hernia is mainly seen in trisomy...
18
100
Prenatal u/s diagnosis of ___ is based on the demonstration of stomach, intestines, or liver in the thorax and the associated mediastinal shift.
diaphragmatic hernia
101
Etiology of ___ defects depends on the interplay of many factors - genetic, environmental, drug exposure, maternal disease state, etc.
heart
102
Heart defects are found in _% of those with trisomy 18 or 13, _% with trisomy 21, and _% of those with turners.
90%, 50%, 40%
103
What marker for Downs is caused by a mineralization within a papillary muscle?
intracardiac echogenic foci
104
What's the difference between omphalocele and gastroschoisis?
Omphalocele has a sac covering.
105
Does the cord insert into the omphalocele or into the umbilicus?
The omphalocele
106
Does the cord insert in the gastroschisis or into the umbilicus?
The umbilicus
107
What do you suspect when the fetal stomach looks collapsed or absent?
esophageal atresia
108
Esophageal atresia is associated with what genetic defect?
trisomy 18
109
T/F? Esophageal atresia causes polyhydramnios.
true
110
Duodenal atresia is associated with ___hydramnios and trisomy ___.
poly-, 21
111
This anomaly presents as multiple fluid-filled loops of bowel in the fetal abdomen.
intestinal obstruction
112
This anomaly may be the result of intra-amniotic hemorrhage or chromosomal defects.
echogenic bowel
113
Mild hydronephrosis is most common in trisomy __.
21
114
Severe hydronephrosis, multicystic kidneys, and renal agenesis are common in trisomy __.
18 & 13.
115
Trisomies 21, 18, triploidy, and turner's are associated with what skeletal anomaly?
short long bones
116
The incidence of IUGR in choromosomal anomalies is about __%.
1%
117
This is any substance causing abnormal structures in an embryo.
tetrogen
118
Tetrogens are divided into what three categories?
1. physical agents
2. drugs and chemical agents
3. maternal factors
119
Radiation and heat are considered what category of tetrogen?
physical agents
120
Some examples of chemical tetrogens?
1. alcohol
2. DES
3. thalidomide
