Congenital defects and their scientific basis

Question 1

Give examples of the aetiologies of structural birth abnormalities

Answer 1

1. Unknown/sporadic = 50%
2. Socioeconomic factors - deprivation, access to care, maternal age
3. Genetics - consanguinity
4. Infections - rubella, syphilis, cytomegalovirus
5. Maternal nutrition status - iodine, folate, obesity, diabetes, xs vit A
6. Environmental - pesticides, medications, alcohol, tobacco, radiation
7. Multifactorial

Question 2

When does organogenesis take place between?

Answer 2

Weeks 2 and 8

- This is the embryonic period

Question 3

When does the ‘foetal period’ begin as the embryonic period ends

Answer 3

Week 9 onwards

Question 4

Give examples of common single primary defects

Answer 4

1. Congenital dislocation of hip
2. Talipes - club foot
3. Cleft lip +- cleft palate
4. Cardiac septal defects - ASD/VSD
5. Neural tube defects

Question 5

What is the difference between a congenital malformation, a disruption and a deformation?

Answer 5

1. A malformation arises during initial formation/morphogenesis of the embryo as a result of genetic and/or environmental factors during organogenesis
2. A disruption is a destructive process which alters normal structures after their formation
3. A deformation is moulding of a body part that has differentiated normally by mechanical forces usually over a long period of time e.g. talipes and congenital hip dislocation

Question 6

What are the 2 basic mechanisms of disruption?

Answer 6

1. Amniotic bands
   - Fibrous bands formed around the baby in amniotic fluid, wrap around limbs and cut them off
2. Cardiovascular accidents
   - E.g. Poland anomaly, due to interruption of subclavian artery vascular supply e.g. due to maternal cocaine use

Question 7

What is a multiple malformation syndrome?

Answer 7

One or more developmental anomalies of two or more systems have occurred and are thought to be due to a common aetiology
- Can be genetic (chromosomal), single gene defects or teratogens

Question 8

Give an example of a multiply malformation syndrome, and signs of this syndrome

Answer 8

Down’s Syndrome

• Flat nasal bridge
• Up-slanting eyes
• Brachycephaly
• Single palmar creases
• Cardiac defects
• Caused by non-disjunction of chromosome 21