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Women's Health > Antenatal Diagnosis of Congenital Abnormalities > Flashcards

Antenatal Diagnosis of Congenital Abnormalities Flashcards

1
Q

What process does cfDNA use to detect abnormalities?

A

Massive parallel sequencing of foetal DNA present in maternal plasma. Alignment of sequencing reads to human genome sequence and determination of relative chromosome representation

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2
Q

When is cfDNA available from?

A

From 9 weeks gestation

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3
Q

What is the turnaround time for cfDNA?

A

~2 weeks (all samples sent overseas)

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4
Q

How does cfDNA compare to other screening strategies for T18, 21?

A

Superior sensitivity and lower false positive rates than other screening strategies

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5
Q

What must be done prior to cfDNA?

A

Dating / viability scan

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6
Q

What is the purpose of the 12 week scna?

A

Diagnosis of foetal defects

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7
Q

Which structural abnormalities may be visualised at 12 week US?

A
  • Anencephaly
  • Alobar holoprosencephaly
  • Exomphalos
  • Gastroschisis
  • Megacystitis
  • Absent hand / foot
  • Polydactyly
  • Diaphragmatic hernia
  • lethal skeletal dysplasia
  • major cong heart defect
  • facial cleft / open spina bifid (rarely detectable)
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8
Q

Why is ductus venosus assessed?

A
  • Positive association between chromosomal abnormalities and abnormal DV flow in first trimester.
  • +ve association with cardiac anomalies
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9
Q

What are the trisomy 18 US anomalies?

A
  • strawberry shaped head
  • choroid plexus cyst
  • absent corpus callous
  • ventriculomegaly
  • facial cleft
  • nuchal oedema
  • cardiac defects
  • oesophageal atresia
  • exomphalos
  • renal defects
  • myelomeningocele
  • talipes / rocker bottom feet
  • overlapping fingers
  • growth restriction
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10
Q

What are the trisomy 13 US anomalies?

A
  • holoprocenphaly
  • anopthalmia / micropthalmia
  • abnormal nose
  • facial clefts
  • cardiac abnormalities
  • omphalocele
  • renal abnormalities
  • postaxial polydactyly
  • myelomeningocele
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11
Q

Triploidy US findings?

A
  • partial mole
  • growth restriction
  • mild ventriculomegaly
  • micrognathia
  • cardiac abnormalities
  • omphalocele
  • small abdo circumference
  • myelomeningocele
  • 3rd-4th fingers syndactyly
  • “Hitch Hiker” toe deformity
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12
Q

What are the types congenital heart defects relating to conotruncual abnormalities?

A
  • transposition of the great arteries
  • truncus arteriosus
  • double outlet of the right ventricle
  • tetralogy of Fallot
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13
Q

What are the congenital heart defects relating to conotruncual abnormalities?

A
  • heterogenous group of defects involving ventricles and great arteries
  • 20-30% cardiac anomalies
  • leading causes of symptomatic cyanotic heart disease
  • CFx within h/d
  • good prognosis with prompt treat hence antenatal diagnosis important
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14
Q

What other abnormalities is congenital diaphragmatic hernia associated with?

A
  • lung hypoplasia

- pulmonary HTN

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15
Q

Incidence congenital diagphragmatic hernia?

A

1:4000

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16
Q

What causes diagphragmatic hernia?

A
  • failed obliteration of pleuro peritoneal canal

- herniation of abdominal organs into the chest

17
Q

which other conditions is diaphragmatic hernia associated with?

A 
Chromosomal anomalies:
-trisomy 18
-trisomy 13
-mosaic tetrasomy 12p (Pallister-Killian)
Other anomalies:
-Iniencephaly
-Fryn
-De Lange
-Beckwith Wiedemann
18
Q

What are the prognostic factors in isolated CDH?

A
  • liver position (2/3 have some liver up)
  • lung to head ratio
  • polyhydramnios
  • mediastinal shift
19
Q

What is ventriculomegaly?

A
  • mean 6-7mm stable across 2nd and 3rd trimesters
  • sign but not diagnosis
  • severe = hydrocephaly
  • mild >10-
20
Q

What is congenital hydrocephaly?

A

-heterogenous group with multiple causes (genetic, infectious, teratogenic, neoplastic)

21
Q

What are the infectious causes of congenital hydrocephaly?

A
  • syphilis
  • toxoplasmosis
  • CMV
  • mumps
  • influenza
22
Q

What is the process of congenital hydrocephaly?

A
  • Disruption of ependymal lining
  • oedema of the WM
  • proliferation of astrocytes and fibrosis
  • thinning of the cortex
  • macrocrania
23
Q

What are the risks associated with mild ventriculomegaly?

A

Increased risk of extracranial anomalies, other CNS anomalies, aneuploidy, congenital infections, perinatal death, abnormal intellectual development

24
Q

When does the callosum develop?

A

Between 10 - 25 weeks

25
Q

What are the obstetric indications for MRI?

A
  • foetal abnormality assessment
  • High risk pregnancies for cerebral ischaemia (multiple pregnancy, TTTS)
  • Foetal surgery assessment
  • placenta accreta, suspected percreta
  • maternal illness
  • post mortem MRI
26
Q

What are the indications for foetal brain MRI?

A

No definitive, US best early / MRI best late. MRI if suspected abnormality on US

  • Mlformation
  • posterior fossa assessment
  • supratentorial anomaly
  • ventriculomegaly
  • high risk foetus (genetic, TTTS, severe anaemia, maternal infection)
27
Q

What is the “structure” of scans throughout pregnancy (timing and purpose etc)?

A

Scan structure
5-10 weeks: number of foetus
11-14: screening for common / severe physical anomalies, T21
14-20: repeat scans, bleeding
20-22: morphology scan (congenital anomalies)
>24w: foetal growth and welbeing

28
Q

Why are does the detection of chromosomal abnormalities decrease with gestational age?

A

Many lethal abnormalities die in utero hence higher rates earlier in pregnancy

29
Q

When should definite testing be offered in DS screening?

A

If final result is higher than 1:300 offer definite testing (risk of miscarriage 1:400 from amnio hence DS risk same / similar as change of harm)

30
Q

What is the DS screening program structure?

A

Women have blood test at 10 weeks; results at 12 week scan

Combine age, NT, gestational age and add blood markers for 1st test (bHCG, PAPPA)

31
Q

What are the blood markers in DS screening?

A
  • bHCG usually double in DS

- PAPPA; pregnancy associated protein A; low in DS

Women's Health (39 decks)

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