A – The reproductive system The structure and function of reproductive organs and gametes and their role in fertilisation Hormonal control of reproduction The biology of controlling fertility Ante- and postnatal screening

KA 4: Ante- and postnatal screening (a) Antenatal screening (c) Pedigree charts (b) Postnatal screening

Learning Outcomes Explain the importance of antenatal screening State the 2 types of ultrasound sound imaging; what they detect and when they would be carried out Give examples of biochemical tests and when they would be carried out State what is meant by a false positive State what is meant by a diagnostic test and why it is carried out Give 2 examples of diagnostic test procedures and describe them State what is meant by rhesus antibody testing and explain why it is used

Think / Pair / Share Why do you think it’s important for pregnant women to receive ante-natal screening? What do you think a future mother and father would want to know about their child? What type of techniques are carried out? What are the names of these techniques?

The Importance of Screening The health of a pregnant woman and her developing fetus can be monitored using a variety of techniques and tests. Antenatal screening (pre-natal) can be used to identify the risk of the fetus developing a genetic disorder or chromosomal abnormality. If necessary, further tests and a prenatal diagnosis can be offered.

1. Ultrasound Imaging Ultrasound scanner Dating Scans 8-14 weeks Anomaly Scans 18-20 weeks

Ultrasound Imaging Decide if each of the following statements is true or false For every statement that is false, correct the word in bold There are 2 types of ultrasound scan – they are dating scans and biochemical scans Anomaly scans are used to detect serious physical problems in the fetus Anomaly scans are carried out at 8-14 weeks Dating scans are used to determine the stage of fertilisation and the due date Dating scans are carried out at 8-14 weeks Dating scans are used in conjunction with biochemical tests for marker chemicals, whose presence can indicate certain medical conditions

Ultrasound Imaging Decide if each of the following statements is true or false For every statement that is false, correct the word in bold There are 2 types of ultrasound scan – they are dating scans and anomaly scans Anomaly scans are used to detect serious physical problems in the fetus Anomaly scans are carried out at 18-20 weeks Dating scans are used to determine the stage of pregnancy and the due date Dating scans are carried out at 8-14 weeks Dating scans are used in conjunction with biochemical tests for marker chemicals, whose presence can indicate certain medical conditions

2. Biochemical tests A woman undergoes many physiological changes during pregnancy. At 16-18 weeks, biochemical tests are carried out to detect the normal changes of pregnancy

2. Biochemical tests A woman undergoes many physiological changes during pregnancy. At 16-18 weeks, biochemical tests are carried out to detect the normal changes of pregnancy Blood pressure Blood type Hormone and metabolism checks Altered blood chemistry

2. Biochemical tests HCG human chorionic gonadotrophin Produced during pregnancy by the implanted cells in the placenta False +ve Ideal time to test In a normal pregnancy – HCG increases during weeks 6-10 then decreases to a steady low level for the length of the pregnancy However, if the fetus has down’s syndrome, the HCG levels will remain high Therefore: biochemical tests must be synchronised with dating scans

Biochemical tests Biochemical tests detect physiological changes of pregnancy. The tests detect marker chemicals such as HCG (Human chorionic gonadotrophin) and AFP (Alpha Fetoprotein). These tests must be carried out an appropriate time, otherwise it would cause a false positive result (testing a substance at the wrong time). Other tests also include general health checks, blood pressure checks, blood type, blood and urine tests.

3. Diagnostic Testing Definitive test to determine if a person is suffering from a particular condition or not Particularly offered to high risk women Age / known health condition A karyotype of the foetal chromosomes must be viewed: Therefore, any condition caused by a chromosome mutation can be identified! Deletion Duplication Translocation

Down’s syndrome Here we can see, there is an extra copy of chromosome 21. BUT…

Familial Down’s syndrome In 5% of cases, the additional chromosome 21 can appear because the majority of chromosome 21 is translocated to chromosome 14.

Chronic myeloid leukaemia

Fragile X Syndrome The Fragile X mental retardation 1 (FMR1) gene on the X chromosome mat fail to be expressed properly. This gene is essential in neural development and results in learning disabilities and cognitive impairment Definitive diagnosis of fragile X syndrome is made through genetic testing to determine the number of CGG repeats (Nucleotide sequence repeat expansion)

How are the foetal chromosomes obtained? Amniocentesis Carried out at 14-16 weeks

How are the foetal chromosomes obtained? Chorionic Villus Sampling (CVS) Carried out as early as 8 weeks but there is a higher rate of miscarriage

Diagnostic Testing A definitive test to determine if a person is suffering from a particular condition or not Particularly offered to ‘high risk’ women Age (i.e. over 35) / known health condition (i.e. diabetic) A karyotype of the foetal chromosomes must be viewed. Foetal chromosomes can be obtained by 2 methods: Amniocentesis Chorionic Villus Sampling (CVS) Card sort activity for table Amniocentesis Both Techniques CVS

4. Rhesus Antibody Testing THINK / PAIR / SHARE RE-CAP ON UNIT 4 - KA 2 What are the 4 blood groups? What do we mean by antigens? What do we mean by antibodies?

Blood groups!

How to test for your blood group https://www.youtube.com/watch?v=mM1UNY6iWnA#t=101

What is this person’s blood group? THIS PERSON IS A+ What is this person’s blood group? The grade I want you all to get 

Agglutination

The Rhesus factor Some people have a further antigen on their blood cells. This is called antigen D and people who possess it are said to be rhesus positive (+ve). Those that lack the antigen D marker are said to be rhesus negative (-ve).

When does the rhesus marker become a PROBLEM? Transfusion of Rh +ve RBC to a Rh –ve person must be avoided And a child born to parents of different rhesus factors may also be at risk…

When does the rhesus marker become a PROBLEM?

When does the rhesus marker become a PROBLEM? The immune system of a Rh -ve recipient would respond to Rh +ve red blood cells and produce anti-D antibodies. These antibodies would persist leaving the person sensitised. Any further transfusion of Rh +ve RBCs to the Rh –ve recipient would result in the person suffering from severe or fatal agglutination.

When does the rhesus marker become a PROBLEM? Anti-rhesus antibodies are given to rhesus- negative mothers after a sensitising event or after birth Generally mothers show no immune response to their fetus although sensitisation to Rhesus antigens can occur

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Learning Outcomes Explain the importance of antenatal screening State the 2 types of ultrasound sound imaging; what they detect and when they would be carried out Give examples of biochemical tests and when they would be carried out State what is meant by a false positive State what is meant by a diagnostic test and why it is carried out Give 2 examples of diagnostic test procedures and describe them State what is meant by rhesus antibody testing and explain why it is used