1. Higher Human Biology Subtopic 12 Ante and postnatal screening
Physiology and Health
Higher Human Biology
Subtopic 12
Ante and postnatal screening

2. Learning Intentions
To explain the use of antenatal screening in the identification of disorders
To describe antenatal screening techniques
To discuss the effects on the Rhesus antigen in pregnancy

3. Antenatal care
Carried out to monitor the health of the mother and foetus during pregnancy.
Checks include :
Height and weight
Blood pressure
Blood type
Urine
General health

4. Antenatal screening
This can identify the risk of a disorder so that further tests can be carried out and a diagnosis given.

5. Screening Vs Diagnostic Tests
Screening Test
Detects signs and symptoms associated with a disorder
Assesses the degree of risk
Diagnostic test
Definite test which establishes, without doubt, whether a person is suffering from a specific condition or disorder

6. Methods of Antenatal Screening
Ultrasound imaging
Biochemical tests
Diagnostic testing
Rhesus antibody testing
Video

7. Ultrasound
A scanner picks up high-frequency sound that bounce off the foetus and create a picture.
Dating Scan
8-14 weeks
Determines the stage of pregnancy
Used to calculate due date alongside biochemical tests
Anomaly Scan
18-20 weeks
Can detect physical abnormalities

9. Biochemical tests
Test blood and urine to detect the normal physiological changes of pregnancy.
Used to detect :
Hypertension
Gestational diabetes
Anaemia
Hyperthyroidism

10. Biochemical tests
A women is offered tests at weeks to check for 3 markers.
A high / low concentration of a marker chemical can differ depends on the stage of pregnancy.

11. Markers
HCG
Normally increases wk 6-10 then decreases to a steady low level
If it remains high it may be a sign of Down’s syndrome
Measuring a substance at the wrong time could lead to a false positive / negative result

12. Diagnostic Tests Offered if : Routine screening has raised a problem
There is a family history of genetic disorders
The women is in a high risk category (e.g 35yrs +)
2 main types of test :
Amniocentesus
CVS

13. Amniocentesus Weeks 14 – 16 Small amount of amniotic fluid taken.
Foetal cells cultured and a karyotype is produced.
A karyotype shows chromosome abnormalities.

14. Normal Karyotypes

15. Down’s Syndrome

17. Kleinfelter's Syndrome
One extra X chromosome

18. Turner’s Syndrome
Only 1 X chromosome

19. CVS Chorionic villus sampling Sample of placental cells taken
Karyotype produced
Increases the risk of miscarriage but can be carried out earlier in pregnancy

22. Rhesus Factor A cell marker found on red blood cells
People with the marker are Rh +ve
People without it are Rh –ve and have anti-D antibodies which will destroy any Rh +ve cells.

23. During pregnancy… 1st pregnancy
A rh –ve mother will produce anti-D antibodies if she comes into contact with her Rh +ve baby …….sensitisation
2nd pregnancy
Her anti-D antibodies will cross the placenta and attach a Rh +ve foetus

26. Treatment
The mother can be given anti-D antibodies to destroy Rh antigens before her immune system kicks in.
The fetus can be given a blood transfusion to replace Rh +ve blood with Rh -ve

27. Post natal screening Screening that takes place after birth
PKU is one of a few inherited disorders that can be successfully treated
PKU is an inborn error of metabolism

28. × × × × × × Phenylketonuria (PKU)
The amino acid phenylalanine is found in the diet. ×
enzyme C × × ×
melanin
(Skin pigment ) ×
Intermediate metabolites
enzyme B
enzyme A ×
phenylalanine
tyrosine
(an amino acid)
In a PKU sufferer the gene that codes for enzyme 1 is defective – what will this result in?
Phenylalanine builds up in the blood.

29. Phenylketonuria (PKU)
Autosomal recessive
Phenylalanine builds up causes mental development to be restricted
PKU is routinely tested for in newly born babies using a Heel prick test.
Treated by following a low phenylalanine diet

31. × PKU Albinism Sufferers have lighter skin.
enzyme C
melanin
(Skin pigment )
Intermediate metabolites
enzyme B
tyrosine
(an amino acid)
Albinism
Albinos cannot make enzyme so don’t produce melanin

32. Learning Intentions
To explain the use of antenatal screening in the identification of disorders
To describe antenatal screening techniques
To discuss the effects on the Rhesus antigen in pregnancy