8B) Antenatal Care - Fetal anomalies/screening Flashcards
(122 cards)
1
Q
Between what CRL measurements can first trimester screening be performed?
A
45-84mm (11+2–>14+1)
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
3
Q
What does free bhCG do in Down’s/Edward’s/Patau?
A
Increased in Down’s.
Reduced in Edward/Patau.
4
Q
What does PAPP-A do in Down’s/Edward’s/Patau?
A
Reduced in all.
5
Q
What is classed as a “high risk” screening result?
A
> 1 in 150
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)
7
Q
What are the measures involved in second trimester screening?
A
Maternal age AFP hCG uE3 Inhibin-A
8
Q
What does AFP go up in?
A
Neural tube defects
9
Q
When does AFP go down?
A
Down’s
10
Q
What is uE3 level in Down’s?
A
Low
11
Q
What is inhibin level in Down’s?
A
Increased
12
Q
How to calculate EDD of pregnancy?
A
Based on CRL unless CRL >84mm in which case use HC.
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
14
Q
Which abnormalities can sometimes be detected on a 1st trimester scan?
A
Spina bifida
Facial cleft
Polydactyly
Renal agenesis
15
Q
Which abnormalities are never detectable on 1st trimester scan?
A
Microcephaly
Agenesis corpus callosum
16
Q
How many pregnancies will be classed as “high risk” based on first trimester screening?
A
3-5%
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
18
Q
Which conditions should have a >95% detection rate?
A
Edwards
Patau
Anencephaly
Gastroschisis
19
Q
Which conditions should have a 90% detection rate?
A
Open spina bifida
20
Q
Which conditions should have a 75-85% detection rate?
A
Cleft lip
Bilateral renal agenesis
Exompholos
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
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
23
Q
Findings which should be reported on 2nd trimester scan
A
NT >6mm Ventriculomegaly (>10mm) Echogenic bowel Renal pelvic dilatation Measurements <5th centile
24
Q
What are lethal skeletal dysplasias?
A
Group of over 200 genetic conditions affecting bone growth and development
25
What is seen in lethal skeletal dysplasias?
Restricted growth with abnormally small limbs/trunk.
| Restricted rib growth prevents lung development.
26
Most common lethal skeletal dysplasias?
Thanatophoric dysplasia
| Type 2 Osteogenesis Imperfecta
27
Overall incidence of lethal skeletal dysplasias
1 in 10,000
28
Prognosis of lethal skeletal dysplasias
No treatment. Fatal either in utero or after birth.
29
How can a formal diagnosis of lethal skeletal dysplasia be made?
Usually impossible via molecular genetics unless known mutation. Formal diagnosis after delivery via postmortem/full body XR, cord blood to genetics.
30
Inheritance of achondroplasia
Autosomal dominant
31
Clinical features of achondroplasia
Homozygous - lethal.
| Heterozygous - short stature but normal intelligence and lifespan.
32
Percentage of cases of achondroplasia which occur as new mutations
80%
33
Which side is congenital diaphragmatic hernia most common on?
Left side (heart displaced to right)
34
Incidence of CDH
4 in 10,000
35
Survival rate of CDH
50%
36
What proportion of infants with CDH have another abnormality?
1/3 associated abnormalities
| 10-20% Chromosomal (Trisomy 18,21, Pallister Killian)
37
Recurrence rate of CDH
2%
38
Incidence of cleft lip
10 in 10,000
39
What proportion of CLP are lip only/palate only/both?
25/25/50
40
Proportion of infants with cleft lip with other abnormalities
16% other structural abnormalities.
| 7% part of syndrome.
41
When to offer karyotype to infant with cleft lip?
If midline, bilateral or other abnormalities.
42
Risk factors for cleft lip
Smoking, alcohol, obesity
43
Recurrence rate of cleft lip
4%
44
Percentage of live births with cardiac abnormalities
1%
45
Percentage of NND associated with cardiac abnormalities
35%
46
What is seen on scan with oesophageal atresia?
Absence of fetal stomach + polyhydramnios.
| If associated tracheal fistula it may not be detected on scan.
47
Proportion of infants with oesophageal fistula who have associated abnormalities
2/3
48
When is duodenal atresia usually detected?
From late second trimester onwards as "double bubble" effect
49
What proportion of infants with duodenal atresia will have trisomy 21?
30%
50
Incidence of anencephaly
5 in 10,000
51
What proportion of infants with anencephaly will be stillborn?
75%
52
Recurrence rate anencephaly
2%
53
Treatment in future pregnancies for mother with previous anencephaly
High dose folic acid
54
Incidence of cystic hygroma
1%
55
What is a complication of cystic hygroma?
Hydrops (with 80-90% mortality rate)
56
What happens in holoprosencephaly?
Abnormality caused by incomplete cleavage of embryonic forebrain meaning there is a communication of ventricles across midline.
57
Associations with HPE
Diabetes
Maternal infections
Drugs (alcohol, aspirin, lithium, retinoids, anticonvulsants)
58
Incidence of HPE
1-2 per 10,000 live births (may be as frequent as 1 in 200 pregnancies)
59
Percentage of infants with HPE which survive to delivery
3%
60
Other structural abnormalities seen with HPE
Midline facial anomalies e.g. midline clefting or cyclopean
61
Incidence of ventriculomegaly
1 in 500
62
Classification of ventriculomegaly
Mild: 10-12mm
Moderate: 12-15mm
Severe >15mm
63
Proportion of mild cases of ventriculomegaly which will have a normal outcome
95%
64
Further investigations in infant with ventriculomegaly
Karyotyping (1-5% chromosomal problems), MRI.
65
Two types of spina bifida
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
Incidence of spina bifida
6 in 10,000 (Closed may be present in 5-10% population)
67
Chiari II malformation
Poor development of cerebellum which is wrapped around spinal cord ("banana sign" on USS) and herniates through foramen magnum therefore blocks CSF --> ventriculomegaly.
68
Recurrence risk of spina bifida
5% after 1 pregnancy
12% after 2 pregnancies
20% after 3 pregnancies
69
Dandy Walker syndrome
Complete cerebellar vermin agenesis
70
Associated chromosomal problem if choroid plexus cysts seen in association with fetal abnormalities
50% chance trisomy 18
71
When does physiological midgut herniation occur?
Weeks 9-12
72
Incidence of omphalocoele
4 in 10,000
73
Percentage of patients with omphalocoele with other abnormalities
80%
| and up to 40% of those thought to be isolated antenatally will have a problem detected after birth
74
What other abnormalities are associated with omphalocoele?
20% cardiac
Chromosomal abnormalities
10% syndrome
75
Mortality of omphalocoele
10% isolate
| >80% if associated anomalies
76
Incidence of gastroschisis
5 in 10,000
77
Association of gastroschisis with other anomalies
Rarely.
| 10% intestinal atresia.
78
Survival of gastroschisis
>90%
79
When can kidneys be visualised on USS?
10 weeks
80
When is non-visualisation of the bladder abnormal?
14/40
81
Incidence of fetal megacystis
1 in 1500
82
Causes of fetal megacystis
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
Prognosis with fetal megacystis
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
Incidence of bilateral renal agenesis
1 in 10,000
85
Implications of bilateral renal agenesis
Neonatal death within few hours.
| In utero - pulmonary hypoplasia, severe talipes and limb conjectures, typical facies, growth restriction.
86
Fix in renal agensis
Up to 1/3 have family history
| Recurrence rate 3% (higher if one pt has unilateral renal agenesis)
87
Most common chromosomal abnormality in UK
Down's
88
Incidence of Down's syndrome
1 in 700live births
89
Percentage of infants with Down's syndrome that miscarry/stillborn
60% miscarry, 20% stillborn
90
What percentage of Down's have congenital heart disease (and which types more common)?
40% congenital heart disease - AVSD, VSD and TOF.
91
What percentage of patients with AVSD will have Down's?
15%
92
What percentage of T21 cataracts?
2%
93
What percentage of T21 epilepsy?
10%
94
What percentage of T21 acute leukaemia?
1%
95
What percentage of T21 early onset dementia?
50% by 50 years
96
What percentage of T21 can attend main stream school?
80%
97
Most common cause of T21
Non-disjunction in meiosis (maternal)
98
Chance of recurrence of trisomies
0.56-0.75% above background risk
99
Prognosis in T21
5% don't survive first year. For the majority life expectancy is into 60s.
100
Incidence of Edwards
1 in 3000
101
Percentage of T18 which miscarry
95%
102
Clinical features of T18
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
Prognosis Edwards
Majority die within first few days of life. <10% survive first year.
104
Cause of T18
Maternal non-disjunction
105
Incidence of Patau syndrome
1 in 5000
106
Prognosis Patau
50% die first month, 75% six months, <5% survive 1 year.
107
Features of T13
```
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
In what percentage of cases can chromosomal array add additional information to karyotype?
3-6%
109
In what percentage of cases can exome sequencing provide additional information?
10%
110
When is cffDNA present?
6-7 weeks
111
What proportion of total plasma DNA is cffDNA?
Approx 10%
112
What percentage of cffDNA testing gives indeterminate results?
3%
113
What affects accuracy of cffDNA?
BMI
Maternal chromosomal abnormalities
Placental mosaicism
Twin pregnancies with single twin demise
114
What percentage of T21 and T13 cases can be detected by cffDNA?
99% T21
| 92% T13
115
Detection rate and false positive rate of:
- Maternal age
- Second trimester screening
- First trimester combined screening
- cffDNA
For Downs
Maternal age: 30% 5%
2nd trimester: 60-75% 5%
1st trimester: 90% 5%
cffDNA: 99% 0.1%
116
Most common indication for invasive testing
To detect aneuploidies
117
Ultrasound markers for Down's that are very sensitive and specific
Absence of nasal bone
Increased resistance in ductus venosus
Tricuspid regurgitation
118
Fetal HR abnormality in Patau
Tachycardia
119
Prevalence of aneuploidies at 11-13 weeks
Edwards: Down's 1:3
Patau: Down's 1:7
120
Minimal fetal fraction for cffDNA detection purposes
4%
121
Twins and cffDNA
Accuracy comparable in mono twins but di twins not reliable.
122
Ideal gestation for cffDNA testing
10 weeks
