Foetal Development

Question 1

1. what is a teratogen?
2. name 6 common teratogens
3. name some of the effects of teratogens

Answer 1

1. an agent administered to the pregnant mother that can directly or indirectly cause structural or functional abnormalities in the foetus or in the child

2. infections
physical agents/chemicals
medicines
alcohol
tobacco
recreational drugs

3. chromosomal abnormalities
impairment of implantation
resorption/abortion of early embryo
structural malformations
IUGR
foetal death
functional impairment in neonate
behavioural abnormalities
mental retardation

Question 2

1. give an example of how teratogens can indirectly affect a foetus
2. what is behavioural tetrology?
3. what is transplacental carcinogenicity?
4. give an example of a transplacental carcinogen

Answer 2

1. affect the mother on which the foetus is dependent. e.g. some recreational drugs cause pyrexia
2. affect on behaviour or functional adaptation of offspring to environment
3. no adverse effects on mother but can cause cancer in offspring
4. diethylstilbestrol - was given to mothers to maintain pregnancy but was found that offspring were developing uterine and vaginal cancers years later.

Question 3

why should polypharmacy be avoided in pregnancy?

Answer 3

often, the combined risk of two agents is greater than the sum of the individual risks for both agents

Question 4

1. name 5 things that affect drug transfer across the placenta
2. how can passive diffusion be increased?

Answer 4

1. molecular weight
lipid solubility
ionisation
protein binding
chemical structure

2. high lipid solubility
   low protein binding
   high maternal blood level of drug

Question 5

1. why may metabolism of a drug be altered in pregnancy?
2. why may renal clearance of a drug be different in pregnancy?
3. why may volume of distribution be different in pregnancy?

Answer 5

1. alteration in maternal liver function and metabolism
2. increased renal blood flow > increased excretion
3. increased body water and increased VoD

Question 6

1. Why are tonic clonic seizures dangerous in pregnancy?
2. Name 3 problems with the use of anti-epileptic medication in pregnancy
3. which antiepileptic medication is contraindicated in pregnancy?

Answer 6

1. increase risk of miscarriage
2. pregnancy can change frequency of seizures
   pharmacokinetic changes can alter the effectiveness of medication
   vomiting in first trimester can also affect the absorption of anti-epileptic medication
3. valproate

Question 7

1. which gestational period is the foetus most susceptible to teratogenic effects?
2. by what gestational week are all internal organs formed?
3. What are the effects of the following drugs in the first trimester:
   a) androgens
   b) oestrogens
   c) warfarin
   d) retinoids
   3) anti-epileptic medications
4. what are the effects of ACE inhibitors after the first trimester?

Answer 7

1. first 12 weeks
2. week 9

3a) virilisation of female foetus
3b) feminisation of male foetus
3c) skeletal defects
3d) cranofacial, cardiovascular and CNS defects
3e) facial defects, neural tube defects, mental retardation

4. oligohydroamnios, lyng and kidney hypoplsia, anuria, growth retardation

Question 8

1. What always needs to be considered when prescribing in pregnancy?
2. Which NSAID should be avoided in pregnancy and why?
3. which drugs are given in pregnancy to manage nausea and vomiting?

Answer 8

1. risk benefit ratio
2. ibuprofen
3. cyclizine or promethazine (first line)
   prochlorperazine or metocloptamide (second line)
   ondansetron (third line)

Question 9

define the following:

1. malformation
2. disruption
3. deformation
4. sequence
5. syndrome

Answer 9

1. primary disturbance in embroyogenesis (made wrong)
2. secondary disturbance due to early influence of external factors (starts out ok but then goes wrong)
3. late changes in previously normal structures
4. one system affected. Has knock on affect on other systems.
5. a set of signs and symptoms that are correlated with each other

Question 10

what are TORCH infections?

Answer 10

toxoplasma
rubella
cytomegalovirus
herpes
syphilis

Question 11

1. what is a polytopic field defect?
2. when do they occur?
3. give two examples

Answer 11

1. scattered pattern of defect caused by disruption of one germ layer at the trilaminar disc phase, thereby affecting all tissues derived from that germ layer.
2. 2-4 weeks
3. di george syndrome - chromosomal abnormality causing congenital heart defects and thymic aplasia
   VACTERAL - vertebral anomalies, anal atresia, cardiac anomalies, tracheo-oesophageal fistula, renal abnormalities, limb abnormalities

Question 12

1. What is a monotopic field defect?
2. when do they occur?
3. give an example

Answer 12

1. localised defect affecting one structure
2. 4-8 weeks
3. cleft lip/palate

Question 13

1. name 2 examples of disruption

2. give 2 examples of deformation

Answer 13

1. amniotic bands
   poland anomaly - underdeveloped chest muscle and short webbed fingers on one side due to interruption of subclavian vascular supply
2. club feet
   developmental dysplasia of the hip

Question 14

1. describe potter’s sequence

2. why is renal function required for lung development?

Answer 14

1. renal agenesis > oligohydraminos > pulmonary hypoplasia > squashed baby with limb position defects
2. foetal urine production makes the amniotic fluid
   amniotic fluid is critical to proper development of lungs
   - provides hydrostatic pressure for alveolar expansion
   - provides proline, a critical amino acid

Question 15

1. What is the triple test for Down’s syndrome comprosed of?
2. what is donw if this test is positive?
3. When is the foetal anomaly scan performed?

Answer 15

1. AFP, estrol and beta hCG
2. mother is sent for amniocentesis/choroid villus testing
3. 20 weeks