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Becks obstetric Qs > Congenital abnormalities and their identification > Flashcards

Congenital abnormalities and their identification Flashcards

1
Q

What is the difference between screening and diagnostic tests?

A

Screening is offered to all women.

Diagnostic tests are offered to those considered to be ‘high risk’ to confirm or refute the possibility.

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2
Q

What is sensitivity and specificity?

A

Sensitivity is the proportion of subjects who have the condition that will test as screen positive for the condition.
Specificity is the proportion of subjects without the condition that will test as screen negative for the condition.

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3
Q

What is negative predictive value and positive predictive value?

A

The NPV is the probability that a subject who is screen negative will not have the condition.
The PPV is the probability that a subject who is screen positive will have the condition.

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4
Q

What are the maternal blood screening tests screening for and what are they looking at?

A

For chromosomal abnormalities (21, 18, 13).
Looking at:
hCG
pregnancy-associated plasma protein A (PAPP-A)
Oestriol
Inhibin A

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5
Q

What is non-invasive prenatal diagnosis?

A

Uses free foetal DNA in the maternal circulation and allows non-invasive antenatal diagnosis of chromosomal abnormalities.
It is expensive and results take >1 week.

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6
Q

How are trisomy risks calculated in pregnancy?

A

Materal blood markers (hCG, oestriol, inhibin A, PAPP-A), maternal age, nuchal translucency –> all independent so used together to calculate risk.

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7
Q

If risk of trisomy is calculated as high, what are the diagnostic tests?

A

Non-invasive prenatal diagnosis using free foetal DNA in maternal blood.
Amniocentesis and chrorionic villus sampling.

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8
Q

What does is nuchal translucency and what does a larger one predict a risk of?

A

It is the space between the skin and the soft tissue overlying the cervical spine.
The larger it is, the higher the risk for trisomies and structural (particularly cardiac) abnormalities.

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9
Q

When do congenital malformations of all organs and systems become detectable?

A

20 week ultrasound scan.

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10
Q

What is associated with the development of polyhydramnios? What is needed?

A

Foetal abnormality.

Needs a repeat detailed ultrasound examination.

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11
Q

What is foetal MRI in utero used for?

A

To aid diagnosis of intracranial lesions and is better at differentiating between different types of soft tissue.

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12
Q

What is amniocentesis? What is it used for?

A

It is a diagnostic test which involves the removal or amniotic fluid using a fine-gauged needle under US guidance.
It enables prenatal diagnosis of chromosomal abnormalities, some infections (CMV and toxoplasmosis), and inherited disorders such as sickle cell anaemia, thalassaemia and cystic fibrosis.

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13
Q

When is it safest to perform amniocentesis and what is the worst complication?

A

From 15 weeks.

Miscarriage - 1% of women do after the procedure, but most are unrelated.

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14
Q

When can chorionic villus sampling be performed, why is it performed and what is the risk?

A

From 11 weeks.
Same reasons as amniocentesis.
Risk of miscarriage - higher than amniocentesis because it is earlier and more difficult.

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15
Q

What is preimplantation genetic diagnosis?

A

Uses IVF. IVF allows cells from a developing embryo to be removed for genetic analysis before the embryo is transferred to the uterus.

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16
Q

What is Down’s syndrome? How does it present?

A

Trisomy 21.

Presents with mental handicap, characteristic facies and 50% have congenital heart disease.

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17
Q

What are the risks of having a Down’s syndrome baby?

A

Advancing maternal age
Previous Down’s syndrome child
Balanced parental translocation (rare)

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18
Q

What are the other trisomies which are screened for with Down’s? How do they differ to Down’s?

A

Chromosome 13 - Patau’s syndrome
Chromosome 18 - Edwards’ syndrome
They will die in utero or at birth due to major structural defects, whereas Down’s children are able to survive.

19
Q

What is Klinefelter’s syndrome?

A

47XXY - males have normal intellect, small testes and are infertile.

20
Q

What is Turner’s syndrome?

A

45 XO - female, have normal intellect, infertile. Characteristic webbed neck.

21
Q

What are the ultrasound risk factors for Down’s syndrome?

A 
Large nuchal translucency
Shortened or absent nasal bone
Some structural abnormalities
Tricuspid regurgitation
Severe foetal growth restriction
22
Q

What are neural tube defects? What are the best known examples?

A

NTDs are the result of failure of closure of the neural tube. Neural tissue is often exposed, allowing degeneration.
Best known examples are spina bifida and anencephaly. The latter is not compatible with life.

23
Q

What reduces the incidence of neural tube defects?

A

3 months preconceptual folic acid supplementation (0.4mg/day) and should be taken by all women considering pregnancy.

24
Q

Neural tube defects reoccur in 1/10th pregnancies, how is this risk reduced?

A

Taking high dose folic acid (5mg/day).

25
Q

What in utero treatments are possible for arrhythmias?

A

Digoxin, flecainide.

26
Q

What are the examples of in utero therapy?

A

Medical
Steroids to mature lungs
Antiarrhythmic drugs
NSAIDs for polyanhydramnios

Minimally invasive
Laser treatment for twin-twin transfusion syndrome
Amnioreduction for polyhydramnios
Pleuroamniotic shunt for hydrops/effusions
Vesicoamniotic shunt for urethral valves
Blood/platelet transfusion
Tracheal occlusion for diaphragmatic hernia
Valvoplasty for critical aortic stenosis
Cord occlusion of monochorionic twins

Open
Neural tube defect surgery

27
Q

What are the two common abdominal wall defects?

A

Exomphalos and gastroschisis

28
Q

What is exomphalos? What is associated with it?

A

Exomphalos is a weakness of the baby’s abdominal wall where the umbilical cord joins it. This weakness allows the abdominal contents, mainly the bowel and the liver to protrude outside the abdominal cavity where they are contained in a loose sac that surrounds the umbilical cord.
50% of affected infants have a chromosomal problem and amniocentesis is offered.

29
Q

What is gastroschisis?

A

Free loops of bowel in the amniotic cavity and is rarely associated with other abnormalities. Postnatal surgery is indicated and >90% survive.

30
Q

What are chest wall defects in foetuses?

A

Diaphragmatic hernia
Pleural effusions
Congenital cystic adenomatous malformations and pulmonary sequestration (visible as chest masses of varying sizes).

31
Q

What is a diaphragmatic hernia? How can survival rate be improved in severe cases?

A

Abdominal contents herniate through the diaphragm into the chest causing pulmonary hypoplasia.
Survival in severe cases is improved by trachea occlusion - where a balloon is placed in the trachea in utero to stimulate lung growth - needs to be removed before or immediately after delivery.

32
Q

What can pleural effusions in utero cause?

A

Hypoplasia of the lungs and hydrops

33
Q

What is hydrops?

A

A condition in the foetus characterised by an accumulation of fluid, or oedema, in at least two foetal compartments.

34
Q

What are some gastrointestinal defects in utero? What are their US appearance?

A

Oesophageal atresia - small/non-visible stomach, polyhydramnios.
Tracheo-oestophageal fistula - small/non-visible stomach, polyhydramnios.
Duodenal atresia - double bubble of stomach and dilated upper duodenum.
Lower gut atresia - dilated bowel.

35
Q

What are common urogenital defects in utero?

A

Hydronephrosis

Posterior urethral valves - obstruct male urethral valves leading to bladder and renal dilation and damage.

36
Q

What are isolated limb abnormalities due to?

A

Often due to amniotic bands, constriction deformities involving the amnion or vascular occlusion.

37
Q

What are the 2 sub-types of hydrops?

A

Immune - due to anaemia and haemolysis as a result of antibodies including Rhesus disease
Non-immune

38
Q

What are the 5 categories of non-immune hydrops?

A 
Chromosomal abnormalities
Structural abnormalities
Cardiac abnormalities or arrhythmias 
Anaemia (causing cardiac failure)
Twin-twin transfusion syndrome
39
Q

When is cure of hydrops possible?

A

When it is caused by twin-twin transfusion syndrome, anaemia (transfusion) or compression by fluid collection such as pleural effusions.

40
Q

What are the complications of polyhydramnios?

A

Preterm labour, maternal discomfort, abnormal lie and malpresentation.

41
Q

What are the risk factors for polyhydramnios?

A

Maternal disorders - diabetes, renal failure, twins, idiopathic, fetal anomaly.

42
Q

What are the clinical features of polyhydramnios?

A

Large for gestational age, hard to palpate foetal parts, maternal discomfort, taut uterus.

43
Q

How do you reduce liquor in polyhydramnios?

A

NSAIDs, amnioreduction or steroids if before 34 weeks.

Becks obstetric Qs (18 decks)

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