Structural Abnormalities

Question 1

List possible CNS structural abnormalities

Answer 1

1) Neural tube defects
2) Anencephaly
3) Ventriculomegaly
4) Akinesia Syndromes

Question 2

Neural Tube Defects

Answer 2

Spina bifida and anencephaly

Failure of closure of neural tube

Neural tissue exposed –> degradation

<1 in 200 pregnancies

Anencephaly is absence of cranium (frog eye on USS)

Preconception Folic Acid 0.4mg/day for 3 months reduces incidence of NTDs

Invx
AFP levels increased
18-21 weeks USS has sensitivity of 95%
Recurrence risk is 1 in 10 (reduced with folic acid)

Question 3

Ventriculomegaly

Answer 3

Commonly lateral ventricles

Often caused by:
NTDs
Aqueduct stenosis or agenesis of corpus callosum

Question 4

Akinesia Syndromes

Answer 4

Akinesia = reduced fetal movments
Often lethal

Abnormal posture

Lack of swallow –> polyhydramnios

Question 5

Cardiac Defects

Answer 5

1% of pregnancies

More common in women with:
Congenital heart disease
Diabetes
Previous affected offspring (3% recurrence rate)
Fetal chromosomal disorder

50% have thickened nuchal tranlucency

Mostly nonlethal and corrected surgically

Valvoplasty for critical aortic stenosis and hypoplastic left heart

Question 6

Abdominal Wall Defects

Answer 6

Exomphalos
Partial extrusion of abdominal contents in peritoneal sac

**50% have chromosomal abnormality
Isolated defects have good prognosis

Gastroschissis
Free loops of bowel in amniotic cavity
Rarely associated with other abnormalities
Common if mother young e.g. 16
>90% survive - requires postnatal surgery

Question 7

Chest Defects

Answer 7

Diaphragmatic hernias
cause abdominal contents to herniate into chest –> pulmonary hypoplasia
Commonly associated with other abnormalities
60% survival
Improve with in utero tracheal occlusion (FETO)

Pleural Effusion
Pulmonary hypoplasia and hydrops
In utero shunting beneficial

Congenital Cystic Adenomatous Malformations & Pulmonary Sequestration
Visible as solid or cystic chest masses of varying size
Good prognosis
Can disappear with time, others need surgery

Question 8

GI Defects

Answer 8

Oesophageal atresia
Tracheo-Oesophageal Fistulae
Stomach non-visible or small
Polyhydramnios as no swallow

Duodenal Atresia
Double bubble sign
Dilated upper stomach
Associated with Down Syndrome
Polyhydramnios

Lower Gut Atresia
Dilated bowel +/- polyhydramnios
Meconium ileus due to CF is common

Question 9

Urogenital Defects

Answer 9

Hydronephrosis 
Mild or severe
Unilateral or bilateral
Due to obstruction or reflux
Children are prone to infection --> renal damage

Posterior urethral valves (obstructing membrane)
Obstructs male urethra
Causes oligohydramnios, bladder and renal dilatation –> damage
Can be lethal, or cause renal damage in early adulthood

Question 10

Thanatophoric Dysplasia

Answer 10

Congenital skeletal abnormality –> generally lethal
disproportionately small ribcage, extremely short limbs and folds of extra skin on the arms and legs
Causes small chest

Question 11

Fetal Hydrops

Answer 11

Occurs when extra fluid accumulates in two or more areas of the fetus
1 in 500 pregnancies
High mortality, therefore rare in later pregnancy

Divided into immune and non-immune

Question 12

Causes of Fetal Hydrops

Answer 12

Immune
–> Anaemia and haemolysis
Rhesus disease
ABO mismatch

Non-Immune

1) Chromosomal abnormalities e.g. Trisomy 21
2) Structural abnormalities e.g. Pleural effusion
3) Cardiac abnormalities or arrhythmias
4) Anaemia e.g. parvovirus, fetomaternal haemorrhage, fetal alpha thalassaemia
5) Twin-twin transfusion syndrome

Question 13

What is the Kleinhauer (KB) test?

Answer 13

Blood test used to measure the amount of fetal hemoglobin transferred from a fetus to a mother’s bloodstream

RCOG Guidelines: The Kleihauer test should be performed in rhesus D (RhD)-negative women to quantify fetomaternal haemorrhage (FMH) in order to gauge the dose of anti-D immunoglobulin (anti-D Ig) required.
The Kleihauer test is not a sensitive test for diagnosing abruption.