Congenital abnormalities

Question 1

Congenital abnormalities Types

Answer 1

Neural tube defects (NTDs)
Cardiac
Abdominal wall defects
Chromosomal abnormalities

Question 2

Neural tube defects (NTDs) definition

Answer 2

Definition: dysraphic malformations result from a failure of the dorsal closure of the fetal neural
tube.

Two main forms of dysraphism are recognized: cranial and spinal. In the third week of
pregnancy called gastrulation, specialized cells on the dorsal side of the embryo begin to change
shape and form the neural tube.

Question 3

Neural tube defects

Types

Answer 3

a. Anencephaly - absence of a major portion of the brain, skull and scalp.

b. Microcephaly - brain does not develop properly resulting in a smaller than normal head.

c. Encephalocele - sac-like protrusions of the brain and the membranes that cover it
through openings in the skull.

d. Holoprosencephaly - prosencephalon fails to develop into two hemispheres.

e. Hydranencephaly - brain’s cerebral hemispheres are absent and remaining
cranial cavity is filled with CSF.

f. Spina bifida
i. Spina bifida occulta
ii. Meningocele
iii. Myelomeningocele

Question 4

Neural tube defects

Causes

Answer 4

Causes:

a. Folic acid deficiency (Vitamin B9) – necessary for DNA synthesis and methylation
processes which are at high demand in the growing embryo

b. Vitamin B12 deficiency
c. Enzymatic variant of MTHFR

Question 5

Neural tube defects
- Diagnosis
- Management

Answer 5

4. Diagnosis:
   a. Ultrasound
   b. Maternal alpha-fetoprotein (AFP) – in serum and amniotic fluid.
5. Management:
   a. Folic acid supplementation – 400mg/day in the pre- and periconceptual periods.
   b. Surgery – in severe cases of spina bifida

Question 6

Congenital cardiac defects

Types

Answer 6

Types:
a. Ventricular septal defects
b. Atrial septal defects
c. Pulmonary stenosis
d. Aortic stenosis
e. Coarctation (of aorta) – can be pre- or post-ductus arteriosus

f. Transpositions (of great vessels) - abnormal spatial arrangement of any of the great
vessels: SVC, IVC, pulmonary artery, pulmonary veins and aorta.

g. Tetralogy of Fallot - pulmonary stenosis, ventricular septal defect, right ventricular
hypertrophy, overriding aorta (blood from both ventricles enter the aorta)

Question 7

Congenital cardiac defects Dx

Answer 7

a. Ultrasound – 18th
-20th weeks using several views:
i. Four chamber view
ii. Left ventricular outflow view
iii. Right ventricular outflow view
iv. Transverse abdominal view

Question 8

Abdominal wall defects

Types

Answer 8

Gastroschisis

Exomphalos (Omphalocele)

Question 9

Gastroschisis

Answer 9

– herniation through rectus abdominis muscle (usually below and to the
right from the umbilical cord) and without peritoneal covering. Size of the hole is
variable so sometimes other organs can be seen but mostly only intestines.

Question 10

Exomphalos (Omphalocele)

Answer 10

– large hernia of the umbilical cord with peritoneal covering

Question 11

Complications

Abdominal wall defects

Answer 11

a. Intrauterine growth restrictions
b. Intestinal atresia
c. Premature birth

Question 12

Chromosomal abnormalities

• Definition
• Types

Answer 12

Definition: Structural or numerical abnormality of the chromosomes. Normal human karyotype
is diploid (2 copies of each chromosome) with 22 somatic pairs and 1 sex pair of chromosomes.

Chromosomal abnormalities identified from the culture and karyotyping of fetal or placental
cells in the amniotic fluid or from the chorionic plate.

Types:
- Down’s syndrome (trisomy 21)
- Turner syndrome
- Klinefelter syndrome
- Edward’s syndrome (Trisomy 18)

Question 13

Down’s syndrome (trisomy 21)

Answer 13

i. Clinically:

• Mental retardation and progressive IQ decline
• Congenital heart diseases
• Flat face and occiput with low flat nose, epicanthal folds
• Short ribs, pelvis, extremities and hands exhibiting simian crease.
• Duodenal stenosis
• Infertility
• High risk for leukemia

ii. Types:
* Nondisjunction (95%) - before conception (all cells are triploid) or after
conception (variable severity depending when the nondisjunction
occurred – leading to mosaic pattern)
* Robertsonian translocation (5%) – between chromosome 14 and 21.

iii. Diagnosis:
* Amniocentesis or chorionic villus sampling
* Nuchal translucency:
o Describes the sonographic appearance of fluid collection under
the skin behind the neck.
o Done in weeks 11-13
o Measure higher than >3mm is abnormal
o Criteria: sagittal section with certain structures that are needed
to be visible, neutral position of fetal head (not hyperflexed or
extended), widest thickness is measured (higher value higher
risk), depends on crown-rump length (CRL)
* In case of increased risk additional finding at weeks 14-20 may include
no or small nasal bone, large ventricles
* Quad test – maternal blood measurements of hCG, AFP, Estriol and
Inhibin-A
* Post birth – physical appearance and karyotyping

Question 14

Turner syndrome

Answer 14

sex chromosome monosomy (X0) and fetus usually undergo
spontaneous abortion.

Question 15

Klinefelter syndrome

Answer 15

sex chromosome trisomy (XXY) due to nondisjunction of first
meiotic division.

Question 16

Edward’s syndrome (Trisomy 18)

Answer 16

– most infants die postnatally.