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Antenatal and Postnatal Screening - Coggle Diagram
Antenatal and Postnatal Screening
Antenatal Screening
Antenatal screening is used to identify risks to the mother or foetus during pregnancy. If a risk is identified further tests may give a prenatal diagnosis
Anomaly Scan
Carried out between 18-20 weeks
May detect serious physical abnormalities
Dating Scan
Carried out between 8-14 weeks
Used to determine stage of pregnancy and due date
Used with tests for marker chemicals which vary during pregnancy
Regular checks are done on the mother's urine and blood to monitor concentrations of marker chemicals. Measuring chemicals at the wrong time can lead to a false positive result. Abnormal levels may indicate pre-eclampsia and down's syndrome.
Diagnostic Testing (antenatal)
Amnioscentesis
Uses a small amount of amniotic fluid to check for genetic disorders
14-16 wekks
Less then 1% risk of miscarriage
Chorionic Villus Sampling
tests cells form the mother's placenta for genetic disorders
early as 8 weeks
Risk of 5% miscarriage
Cells are cultured and karyotyped
Can diagnose conditions such as down's syndrome, turner's syndrome and klinefelter's syndrome
Postnatal Screening
Phenylketonuria (PKU)
Autosomal recessive - requires two recessive alleles
Substitution mutation
Results in the enzyme needed to concert phenylalanine into tyrosine being non-functional
Tested for with a heel-prick test
Can be treated with a low phenylalanine diet
Single-gene Disorders
Autosomal recessive
: require two recessive alleles to be affected. Both genders affected equally and characteristic may skip generations. An example is Cystic Fibrosis, which mainly affects the lungs and digestive system, potentially becoming clogged with thick sticky mucus.
Autosomal Dominant
: only requires one allele to be affected. Affects both genders equally. An example is Huntington's disease, which causes damage to brain cells.
Incomplete Dominance
: in some situations the dominant allele may not fully express itself (red flower + white flower = pink flower)
Sex-linked Recessive Inheritance
: An example is Haemophilia, where people are unable to clot their blood resulting from excessive bleeding. Caused by a recessive allele on the X chromosome. Males affected more because they only need one recessive allele. Woman with one recessive allele are known as carriers.