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OB/GYN Scanning > Chromosomal Defects > Flashcards

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

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2
Q

U/s screening is based onthe fact that most fetuses with chromosomal abnormalities have…

A

major structural malformations or minor ‘markers’

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3
Q

The risk for many of the chromosomal defects increases with…

A

age.

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4
Q

Major chromosomal defects are associated with…

A
  1. multiple antomic abnormalites
  2. mental limitations
  3. high mortality rate
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5
Q

Genetic disease may be the result of…

A
  1. abnormal # of chormosomes
  2. abnormal structure of chromosomes
  3. single gene defect (dominant or recessive)
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6
Q

The probablity of passing on a dominant genetic trait to your offspring is…

A

50%

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7
Q

The probablity of passing on a recessive genetic trait to your offspring is…

A

25%

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8
Q

This is the complete set of chromosomes in a cell, often arranged in pairs for analysis.

A

karyotype

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9
Q

This is a normal balanced set of chromosomes.

A

euploid

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10
Q

This is an unbalanced set of chromosomes.

A

aneuploid

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11
Q

This is the presence of an extra chromosome.

A

trisomy

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12
Q

This is the entire physical and physiologic makeup of an individual determined both geneticlly & environmentally.

A

phenotype

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13
Q

This is the genetic composition of an individual.

A

genotype

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14
Q

What increases the risk of trisomy?

A
  1. older mother

2. previous trisomy (another .75%)

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15
Q

A major congenitial anomaly is found in…

A

3:100 births.

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16
Q

__% births are complicated by minor birth defects.

A

10-15

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17
Q

In the first trimester chromosomal abnormaliites are determined by…

A
  1. nuchal translucency
  2. free beta-hCG and PAPP-A
  3. CVS-Chorionic Villus Sampling
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18
Q

This scan measures the fluid filled area at the back of the neck between 11.5 - 13.5 weeks.

A

nuchal translucency

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19
Q

The nuchal translucency scan measures the fluid filled area at the back of the neck between __ weeks.

A

11.5 -13.5

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20
Q

Low levels of beta-hCG and PAPP-A may indicate…

A
  1. abnormal implantation
  2. poor placental development
  3. a risk for trisomy 18
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21
Q

The blood test and the nuchal translucency together can detect about ___ of fetuses with Downs and Edwards.

A

85%

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22
Q

When abnormal blood tests and translucencies are obtained, patient’s are offered…

A

a CVS to determine chromosomal defects.

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23
Q

T/F? Neural tube defects can be diagnosed with CVS.

A

FALSE, cannot

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24
Q

A CVS is performed between ___ weeks.

A

9-12

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25
Q

Results from CVS are usually back in ___ days.

A

2-3

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26
Q

In the 2nd and 3rd trimester, chromosomal abnormalities are determined by…

A
  1. multiple marker screening

2. amniocentesis

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27
Q

These biochemical screening tests have been developed to find fetal anomalies.

A

multiple marker screening

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28
Q

This test screens for a protein normally produced by the fetal liver.

A

MS-AFP

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29
Q

This test screens for a hormone produced within the placenta.

A

hCG

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30
Q

This test screens for an estrogen produced by both the fetus and the placenta.

A

uE3 (unconjugated estriol)

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31
Q

What might be wrong if MS-AFP is increased?

A
  1. wrong dates
  2. multiple gestations
  3. open neural tube defects
  4. ventral wall defects
  5. amniotic band syndrome
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32
Q

What might be wrong if MS-AFP is decreased?

A
  1. wrong dates
  2. trisomy 13. 18, or 21
  3. fetal demise
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33
Q

MS-AFP is measured in…

A

“MOM” (multiples of the median)

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34
Q

An elevated MS-AFP =

A

equal to or greater than 2 MOM

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35
Q

What might be wrong if hCG is elevated?

A

Downs or trisomy 21

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36
Q

What might be wrong if uE3 is decreased?

A

Downs or trisomy 21

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37
Q

This is offered to evaluate amniotic fluid levels of AFP and for fetal karyotyping.

A

amniocentesis

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38
Q

What might be wrong if amnio-AFP is elevated?

A

occult neural tube defect

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39
Q

Amniocentesis is usually performed around…

A

16 weeks.

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40
Q

Results from amniocentesis are usually back within..

A

7-10 days.

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41
Q

Which genetic testing procedure can be performed the earliest in a pregnacy to determine chromosomal bnormalities and karyotyping?

A

CVS

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42
Q

Trisomy 21 (Downs) occurs in how many births?

A

1:800

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43
Q

___ are the major cause of infant mortality in Downs syndrome.

A

heart anomalies

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44
Q

Downs syndrome patients suffer from…

A
  1. heart anomalies
  2. mental limitations
  3. respiratory problems
  4. eye problems
  5. premature aging
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45
Q

How many cases of trisomy 21 are caught by u/s exam?

A

3:4

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46
Q

What are the most common u/s findings indicated trisomy 21?

A
  1. nuchal fold >6 mm at 15-21 weeks
  2. cardiac defects
  3. duodenal atresia
  4. short femur and humerus
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47
Q

Trisomy 21 infants may present with what physical features?

A
  1. flattened nasal bridge
  2. round small ears
  3. protruding tongue
  4. echogenic bowel
  5. sandal gap
  6. clinodactyly
  7. simian crease
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48
Q

What sonographic sign indicates duodenal atresia?

A

‘double-bubble’ sign

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49
Q

This is the most common trisomy.

A

21 or Downs

50
Q

This is the 2nd most common trisomy.

A

18 or Edwards

51
Q

Edwards is considered a lethal anomaly with __ of infants dying within the first year.

52
Q

Infants with Edwards may present with what physical features?

A
  1. clinodactyly
  2. omphalocele**
  3. choroid plexus cysts
  4. strawberry-shaped head
  5. micronathia (weak chin)
53
Q

This trisomy is also called Patau’s Syndrome.

A

Trisomy 13

54
Q

Infants with Patau’s may present with what physical features?

A
  1. holoprosencephaly*
  2. polydactyly
  3. cleft lip
  4. proboscis
55
Q

This chromosomal defect occurs as a result of an ova being fertilized by two sperm.

56
Q

Triploidy may occur in _% of conceptions and most fetuses will ___ in the first trimester.

A

1%, spontaneously abort

57
Q

T/F? Triploidy is considered a lethal condition.

58
Q

This syndrome is a genetic abnormality marked by the complete or partial absence of an X chromosome.

A

Turner’s

59
Q

The prognosis for Turner’s is especially grave when the fetus presents with a large ___ and edema or hydrops.

A

cystic hygroma

60
Q

How many infants with Patau’s die within the first year?

61
Q

People with Turner’s who survive infancy often have these anomalies…

A
  1. immature sexual development
  2. amenorrhea
  3. short stature
  4. webbed neck*
  5. shield-shaped chest
  6. normal intelligence
62
Q

This condition of dilated lateral cerebral ventricles can be identified via prenatal u/s.

A

ventriculomegaly

63
Q

Ventiriculomegaly is commonly caused by…

A
  1. choromosomal or genetic defect
  2. intrauterine hemorrhage or infection
  3. who knows?
64
Q

Ventriculomegaly is seen with what common chromosomal defects?

A

trisomies 21, 18, 13, & triploidy

65
Q

A lateral ventricle with a diameter between ___ is usually considered mild or borderline ventriculomegaly.

66
Q

A lateral ventricle with a diameter of ___ is usually considered hydrocephalus.

A

greater than 15 mm

67
Q

This is a structural anomaly of the brain in which the developing forebrain fails to divide into two separate hemispheres and ventricles.

A

holoprosencephaly (HPE)

68
Q

HPE is most commonly seen in the chromosomal defects of ___

A

trisomies 13 & 18

69
Q

The hallmark of HPE is the absence of…

A

cavum septum pellucida & the lack of formation of midline structures.

70
Q

What are the three degrees of HPE?

A
  1. alobar
  2. semilobar
  3. lobar
71
Q

This is the most severe degree of HPE characterized by a monoventricular cavity and fusion of the thalami.

72
Q

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.

73
Q

This is the mildest degree of HPE with normal separation of ventricles and thalami but the absence of the septum pellucidum.

74
Q

These degrees of HPE are often accompanied by microcephaly and facial abnormalities.

A

alobar and semilobar

75
Q

Prenatal diagnoses of this brain abnormality is based on the identification of a disproportionately reduced head circumference.

A

microencephaly

76
Q

T/F? In more than 80% of microencephaly cases, here is severe mental limitations.

A

FALSE, 50%

77
Q

Choroid plexus cysts are found in about 2% of fetuses at __ weeks gestation, but in most cases they resolve by 28 weeks.

A

16-24 weeks

78
Q

If choroid plexus cysts are ___, the risk of trisomy 18 is increased only marginally.

79
Q

This condition can be suspected by the absence of the cavum eptum pellucidum and enlargement of the posterior horn of the lateral ventricle.

A

agenesis of the corpus callosum

80
Q

This is the bundle of fibers that connects the two cerebral hemispheres.

A

corpus callosum

81
Q

The corpus callosum develops at ___ weeks gestation.

A

12-18 weeks

82
Q

T/F? In about 90% of isolated agenesis of corpus callosum cases, the development is normal.

83
Q

This refers to the spectrum of abnormalities of the cerebellar vermis, cystic dilation of the 4th ventricle, and enlargement of the cisterna magna.

A

dandy-walker syndrome

84
Q

The overall incidence of of chromosomal defects in Dandy-Walker Syndrome is about __%, usually trisomies ___.

A

40%; 18, 13 or triploidy

85
Q

In Dandy-Walker Syndrome, an enlarged cisterna magna is diagnosed if the distance from the vermis to the inside of the skull is…

A

more than 10 mm.

86
Q

T/F? In Dandy-Walker Syndrome there is a cystic dilation of the third ventricle.

A

FALSE, fourth

87
Q

T/F? In about 80% of trisomy 21 cases, there is a strawberry shaped head.

A

FALSE, trisomy 18

88
Q

This abnormality is a relative shortening of the occipitofrontal diameter.

A

brachycephaly

89
Q

Brachycephaly is found in cases of…

A

Robert’s and Down’s

90
Q

This facial abnormality is found in about 40% of chromosomal defects and most commonly in trisomies 13 & 18.

A

facial cleft

91
Q

This facial abnormality is a moderate posterior position of the mandible.

A

micrognathia

92
Q

Micrognathia is found mainly in trisomies…

A

18 and triploidy.

93
Q

This facial abnormality is a common feature of trisomy 21.

A

macroglossia

94
Q

This facial abnormality is defined as a nasal bone that is not visible or with a length of less than 2.5 mm.

A

nasal hypoplasia

95
Q

This is a 2nd trimester marker that is the single most sensitive impact on screening for trisomy 21.

A

nasal hypoplasia

96
Q

In about 85% of neonates with trisomy __, the ear length is below the 3rd percentile.

97
Q

This is a developmental abnormality of the lymphatic system.

A

cystic hygroma

98
Q

Cystic hygroma is almost always seen in ___ syndrome.

99
Q

Diaphragmatic hernia is mainly seen in trisomy…

100
Q

Prenatal u/s diagnosis of ___ is based on the demonstration of stomach, intestines, or liver in the thorax and the associated mediastinal shift.

A

diaphragmatic hernia

101
Q

Etiology of ___ defects depends on the interplay of many factors - genetic, environmental, drug exposure, maternal disease state, etc.

102
Q

Heart defects are found in _% of those with trisomy 18 or 13, _% with trisomy 21, and _% of those with turners.

A

90%, 50%, 40%

103
Q

What marker for Downs is caused by a mineralization within a papillary muscle?

A

intracardiac echogenic foci

104
Q

What’s the difference between omphalocele and gastroschoisis?

A

Omphalocele has a sac covering.

105
Q

Does the cord insert into the omphalocele or into the umbilicus?

A

The omphalocele

106
Q

Does the cord insert in the gastroschisis or into the umbilicus?

A

The umbilicus

107
Q

What do you suspect when the fetal stomach looks collapsed or absent?

A

esophageal atresia

108
Q

Esophageal atresia is associated with what genetic defect?

A

trisomy 18

109
Q

T/F? Esophageal atresia causes polyhydramnios.

110
Q

Duodenal atresia is associated with ___hydramnios and trisomy ___.

111
Q

This anomaly presents as multiple fluid-filled loops of bowel in the fetal abdomen.

A

intestinal obstruction

112
Q

This anomaly may be the result of intra-amniotic hemorrhage or chromosomal defects.

A

echogenic bowel

113
Q

Mild hydronephrosis is most common in trisomy __.

114
Q

Severe hydronephrosis, multicystic kidneys, and renal agenesis are common in trisomy __.

115
Q

Trisomies 21, 18, triploidy, and turner’s are associated with what skeletal anomaly?

A

short long bones

116
Q

The incidence of IUGR in choromosomal anomalies is about __%.

117
Q

This is any substance causing abnormal structures in an embryo.

118
Q

Tetrogens are divided into what three categories?

A
  1. physical agents
  2. drugs and chemical agents
  3. maternal factors
119
Q

Radiation and heat are considered what category of tetrogen?

A

physical agents

120
Q

Some examples of chemical tetrogens?

A
  1. alcohol
  2. DES
  3. thalidomide

OB/GYN Scanning (14 decks)

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