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Laura MRCOG Part 2 > 8B) Antenatal Care - Fetal anomalies/screening > Flashcards

8B) Antenatal Care - Fetal anomalies/screening Flashcards

1
Q

Between what CRL measurements can first trimester screening be performed?

A

45-84mm (11+2–>14+1)

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2
Q

What are the measures involved in first trimester screening?

A

Maternal age (or donor age if oocyte donated)
Nuchal translucency
free bhCG
PAPP-A

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3
Q

What does free bhCG do in Down’s/Edward’s/Patau?

A

Increased in Down’s.

Reduced in Edward/Patau.

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4
Q

What does PAPP-A do in Down’s/Edward’s/Patau?

A

Reduced in all.

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5
Q

What is classed as a “high risk” screening result?

A

> 1 in 150

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6
Q

When should second trimester screening be performed?

A

If CRL >84mm then pregnancy dated based on HC > 101mm. (14+2 until 20+0)

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7
Q

What are the measures involved in second trimester screening?

A 
Maternal age
AFP
hCG
uE3
Inhibin-A
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8
Q

What does AFP go up in?

A

Neural tube defects

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9
Q

When does AFP go down?

A

Down’s

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10
Q

What is uE3 level in Down’s?

A

Low

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11
Q

What is inhibin level in Down’s?

A

Increased

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12
Q

How to calculate EDD of pregnancy?

A

Based on CRL unless CRL >84mm in which case use HC.

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13
Q

Which abnormalities can always be detected on a 1st trimester scan?

A

Anencephaly
Body stalk anomaly (abdominal organs develop outside body and attach to placenta)
Megacystis
Alobar holoprosencephaly

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14
Q

Which abnormalities can sometimes be detected on a 1st trimester scan?

A

Spina bifida
Facial cleft
Polydactyly
Renal agenesis

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15
Q

Which abnormalities are never detectable on 1st trimester scan?

A

Microcephaly

Agenesis corpus callosum

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16
Q

How many pregnancies will be classed as “high risk” based on first trimester screening?

A

3-5%

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17
Q

What are the 11 conditions to be detected on a second trimester ultrasound?

A 
Edwards
Patau
Anencephaly
Gastroschisis
Open spina bifida
Cleft lip
Bilateral renal agesnsis
Exompholos
Serious cardiac abnormalities (TGA, AVSD, TOF, hypo plastic L heart)
Lethal skeletal dysplasia
Diaphragmatic hernia
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18
Q

Which conditions should have a >95% detection rate?

A

Edwards
Patau
Anencephaly
Gastroschisis

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19
Q

Which conditions should have a 90% detection rate?

A

Open spina bifida

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20
Q

Which conditions should have a 75-85% detection rate?

A

Cleft lip
Bilateral renal agenesis
Exompholos

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21
Q

Which conditions should have a 50-60% detection rate?

A

Serious cardiac abnormalities (TGA, AVSD, TOF, hypoplastic left heart)
Lethal skeletal dysplasia
Diaphragmatic hernia

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22
Q

Normal variants which don’t need reporting from 2nd trimester scan if no other concerning features

A

Choroid plexus cyst
Dilated cisterns magna
Echogenic focus in heart
Two vessel cord

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23
Q

Findings which should be reported on 2nd trimester scan

A 
NT >6mm
Ventriculomegaly (>10mm)
Echogenic bowel
Renal pelvic dilatation
Measurements <5th centile
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24
Q

What are lethal skeletal dysplasias?

A

Group of over 200 genetic conditions affecting bone growth and development

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25
Q

What is seen in lethal skeletal dysplasias?

A

Restricted growth with abnormally small limbs/trunk.

Restricted rib growth prevents lung development.

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26
Q

Most common lethal skeletal dysplasias?

A

Thanatophoric dysplasia

Type 2 Osteogenesis Imperfecta

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27
Q

Overall incidence of lethal skeletal dysplasias

A

1 in 10,000

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28
Q

Prognosis of lethal skeletal dysplasias

A

No treatment. Fatal either in utero or after birth.

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29
Q

How can a formal diagnosis of lethal skeletal dysplasia be made?

A

Usually impossible via molecular genetics unless known mutation. Formal diagnosis after delivery via postmortem/full body XR, cord blood to genetics.

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30
Q

Inheritance of achondroplasia

A

Autosomal dominant

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31
Q

Clinical features of achondroplasia

A

Homozygous - lethal.

Heterozygous - short stature but normal intelligence and lifespan.

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32
Q

Percentage of cases of achondroplasia which occur as new mutations

A

80%

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33
Q

Which side is congenital diaphragmatic hernia most common on?

A

Left side (heart displaced to right)

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34
Q

Incidence of CDH

A

4 in 10,000

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35
Q

Survival rate of CDH

A

50%

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36
Q

What proportion of infants with CDH have another abnormality?

A

1/3 associated abnormalities

10-20% Chromosomal (Trisomy 18,21, Pallister Killian)

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37
Q

Recurrence rate of CDH

A

2%

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38
Q

Incidence of cleft lip

A

10 in 10,000

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39
Q

What proportion of CLP are lip only/palate only/both?

A

25/25/50

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40
Q

Proportion of infants with cleft lip with other abnormalities

A

16% other structural abnormalities.

7% part of syndrome.

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41
Q

When to offer karyotype to infant with cleft lip?

A

If midline, bilateral or other abnormalities.

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42
Q

Risk factors for cleft lip

A

Smoking, alcohol, obesity

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43
Q

Recurrence rate of cleft lip

A

4%

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44
Q

Percentage of live births with cardiac abnormalities

A

1%

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45
Q

Percentage of NND associated with cardiac abnormalities

A

35%

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46
Q

What is seen on scan with oesophageal atresia?

A

Absence of fetal stomach + polyhydramnios.

If associated tracheal fistula it may not be detected on scan.

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47
Q

Proportion of infants with oesophageal fistula who have associated abnormalities

A

2/3

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48
Q

When is duodenal atresia usually detected?

A

From late second trimester onwards as “double bubble” effect

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49
Q

What proportion of infants with duodenal atresia will have trisomy 21?

A

30%

50
Q

Incidence of anencephaly

A

5 in 10,000

51
Q

What proportion of infants with anencephaly will be stillborn?

A

75%

52
Q

Recurrence rate anencephaly

A

2%

53
Q

Treatment in future pregnancies for mother with previous anencephaly

A

High dose folic acid

54
Q

Incidence of cystic hygroma

A

1%

55
Q

What is a complication of cystic hygroma?

A

Hydrops (with 80-90% mortality rate)

56
Q

What happens in holoprosencephaly?

A

Abnormality caused by incomplete cleavage of embryonic forebrain meaning there is a communication of ventricles across midline.

57
Q

Associations with HPE

A

Diabetes
Maternal infections
Drugs (alcohol, aspirin, lithium, retinoids, anticonvulsants)

58
Q

Incidence of HPE

A

1-2 per 10,000 live births (may be as frequent as 1 in 200 pregnancies)

59
Q

Percentage of infants with HPE which survive to delivery

A

3%

60
Q

Other structural abnormalities seen with HPE

A

Midline facial anomalies e.g. midline clefting or cyclopean

61
Q

Incidence of ventriculomegaly

A

1 in 500

62
Q

Classification of ventriculomegaly

A

Mild: 10-12mm
Moderate: 12-15mm
Severe >15mm

63
Q

Proportion of mild cases of ventriculomegaly which will have a normal outcome

A

95%

64
Q

Further investigations in infant with ventriculomegaly

A

Karyotyping (1-5% chromosomal problems), MRI.

65
Q

Two types of spina bifida

A

Occulta: Vertebra has not developed properly but defect is covered over by skin.

Aperta: Herniation of a sac containing meninges +/- nerves out of opening in spine.

66
Q

Incidence of spina bifida

A

6 in 10,000 (Closed may be present in 5-10% population)

67
Q

Chiari II malformation

A

Poor development of cerebellum which is wrapped around spinal cord (“banana sign” on USS) and herniates through foramen magnum therefore blocks CSF –> ventriculomegaly.

68
Q

Recurrence risk of spina bifida

A

5% after 1 pregnancy
12% after 2 pregnancies
20% after 3 pregnancies

69
Q

Dandy Walker syndrome

A

Complete cerebellar vermin agenesis

70
Q

Associated chromosomal problem if choroid plexus cysts seen in association with fetal abnormalities

A

50% chance trisomy 18

71
Q

When does physiological midgut herniation occur?

A

Weeks 9-12

72
Q

Incidence of omphalocoele

A

4 in 10,000

73
Q

Percentage of patients with omphalocoele with other abnormalities

A

80%

and up to 40% of those thought to be isolated antenatally will have a problem detected after birth

74
Q

What other abnormalities are associated with omphalocoele?

A

20% cardiac
Chromosomal abnormalities
10% syndrome

75
Q

Mortality of omphalocoele

A

10% isolate

>80% if associated anomalies

76
Q

Incidence of gastroschisis

A

5 in 10,000

77
Q

Association of gastroschisis with other anomalies

A

Rarely.

10% intestinal atresia.

78
Q

Survival of gastroschisis

A

> 90%

79
Q

When can kidneys be visualised on USS?

A

10 weeks

80
Q

When is non-visualisation of the bladder abnormal?

A

14/40

81
Q

Incidence of fetal megacystis

A

1 in 1500

82
Q

Causes of fetal megacystis

A

Usually due to outflow obstruction (males with posterior urethral valves, or urethral agenesis).

Chromosomal abnormalities in 25% if bladder diameter 7-15mm or 10% if >15mm

83
Q

Prognosis with fetal megacystis

A

If chromosomes are normal and bladder 7-15mm then there’ll be spontaneous resolution in 90%. If >15mm likely progressive obstructive uropathy leading to hydronephrosis and dysplasia +/- pulmonary hypoplasia.

84
Q

Incidence of bilateral renal agenesis

A

1 in 10,000

85
Q

Implications of bilateral renal agenesis

A

Neonatal death within few hours.

In utero - pulmonary hypoplasia, severe talipes and limb conjectures, typical facies, growth restriction.

86
Q

Fix in renal agensis

A

Up to 1/3 have family history

Recurrence rate 3% (higher if one pt has unilateral renal agenesis)

87
Q

Most common chromosomal abnormality in UK

A

Down’s

88
Q

Incidence of Down’s syndrome

A

1 in 700live births

89
Q

Percentage of infants with Down’s syndrome that miscarry/stillborn

A

60% miscarry, 20% stillborn

90
Q

What percentage of Down’s have congenital heart disease (and which types more common)?

A

40% congenital heart disease - AVSD, VSD and TOF.

91
Q

What percentage of patients with AVSD will have Down’s?

A

15%

92
Q

What percentage of T21 cataracts?

A

2%

93
Q

What percentage of T21 epilepsy?

A

10%

94
Q

What percentage of T21 acute leukaemia?

A

1%

95
Q

What percentage of T21 early onset dementia?

A

50% by 50 years

96
Q

What percentage of T21 can attend main stream school?

A

80%

97
Q

Most common cause of T21

A

Non-disjunction in meiosis (maternal)

98
Q

Chance of recurrence of trisomies

A

0.56-0.75% above background risk

99
Q

Prognosis in T21

A

5% don’t survive first year. For the majority life expectancy is into 60s.

100
Q

Incidence of Edwards

A

1 in 3000

101
Q

Percentage of T18 which miscarry

A

95%

102
Q

Clinical features of T18

A

Head: Strawberry skull, choroid plexus cysts, enlarged cisterna magna.
Face/Neck: Micrognathia, low-set ears, cleft lip/palate
Hands/Feet: Flexed/overlapping fingers, rocker-bottom feet.
Cardiac: VSD/AVSD/double outlet R ventricle
Abdomen: Exompholos
Thorax: Diaphragmatic hernia
General: Growth restriction, polyhydramnios
Profound developmental delay

103
Q

Prognosis Edwards

A

Majority die within first few days of life. <10% survive first year.

104
Q

Cause of T18

A

Maternal non-disjunction

105
Q

Incidence of Patau syndrome

A

1 in 5000

106
Q

Prognosis Patau

A

50% die first month, 75% six months, <5% survive 1 year.

107
Q

Features of T13

A 
Head: Holoprosencephaly, genesis corpus callous, dandy walker syndrome.
Face: Cleft lip and palate.
Hands/feet: Polydactyly
Heart: AVSD/VSD/hypoplastic left heart
Kidney: Renal cysts/hydronephrosis
Growth restriction
108
Q

In what percentage of cases can chromosomal array add additional information to karyotype?

A

3-6%

109
Q

In what percentage of cases can exome sequencing provide additional information?

A

10%

110
Q

When is cffDNA present?

A

6-7 weeks

111
Q

What proportion of total plasma DNA is cffDNA?

A

Approx 10%

112
Q

What percentage of cffDNA testing gives indeterminate results?

A

3%

113
Q

What affects accuracy of cffDNA?

A

BMI
Maternal chromosomal abnormalities
Placental mosaicism
Twin pregnancies with single twin demise

114
Q

What percentage of T21 and T13 cases can be detected by cffDNA?

A

99% T21

92% T13

115
Q

Detection rate and false positive rate of:

  • Maternal age
  • Second trimester screening
  • First trimester combined screening
  • cffDNA

For Downs

A

Maternal age: 30% 5%
2nd trimester: 60-75% 5%
1st trimester: 90% 5%
cffDNA: 99% 0.1%

116
Q

Most common indication for invasive testing

A

To detect aneuploidies

117
Q

Ultrasound markers for Down’s that are very sensitive and specific

A

Absence of nasal bone
Increased resistance in ductus venosus
Tricuspid regurgitation

118
Q

Fetal HR abnormality in Patau

A

Tachycardia

119
Q

Prevalence of aneuploidies at 11-13 weeks

A

Edwards: Down’s 1:3
Patau: Down’s 1:7

120
Q

Minimal fetal fraction for cffDNA detection purposes

A

4%

121
Q

Twins and cffDNA

A

Accuracy comparable in mono twins but di twins not reliable.

122
Q

Ideal gestation for cffDNA testing

A

10 weeks

Laura MRCOG Part 2 (56 decks)

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