KA4 - Ante And Postnatal Screening Flashcards
(27 cards)
What is antenatal screening?
Antenatal screening identifies the risk of a disorder so that further tests can be carried out and a prenatal diagnosis can be offered
What is an ultrasound scan?
Ultrasound scans use sound waves to build a picture of the developing foetus in the uterus
What are the 2 different ultrasound scans?
Dating scan
Anomaly scan
What is a dating scan?
Dating scans which determine the stage of pregnancy and due date are used with tests for marker chemicals which vary normally during pregnancy
When does a dating scan take place?
Between 8-14 weeks
What is an anomaly scan?
Anomaly scans may detect serious physical abnormalities in the foetus
When does an anomaly scan take place?
Between 18-20 weeks
What are biochemical tests?
Routine blood and urine tests are carried out throughout pregnancy to monitor the concentrations of marker chemicals
What is diagnostic testing?
An atypical concentration can lead to diagnostic testing to determine if the foetus has a medical condition.
As a result of routine screening or for individuals in high risk categories, further tests may be offered. What may these tests include?
Amniocentesis
Chronic villus sampling
What is used to produce a karyotype?
Cells from samples from amniocentesis or chronic villus sampling can be cultured to obtain sufficient cells to produce a karyotype
What is a karyotype?
A karyotype is an image of an individuals chromosomes arranged in homologous pairs
What is a karyotype used to identify?
Anomalies in terms of the numbers or structures of chromosomes
Give an account of amniocentesis (4)
- amniocentesis involves the withdrawal of amniotic fluid containing foetal cells
- it is carried out around 14-16 weeks of pregnancy
- cells are cultured and karyotype examined
- the process takes 2 weeks
Give an account of chronic villus sampling (5)
- CVS involves a sample of placental cells being removed
- carried out 8 weeks into pregnancy
- higher risk of miscarriage (1-2%)
- earlier termination possible
- karyotyping can be preformed on the foetal cells immediately
What is a pedigree chart?
Pedigree charts are used to analyse patterns of inheritance in genetic screening and counselling.
How is a pedigree chart used?
The information is used by genetic counsellors to advise parents of the possibility of passing on a genetic condition to their child
What is a carrier?
A carrier carries one copy of the faulty gene but doesn’t show the genetic condition. They can however pass the gene to their offspring.
What is an autosome?
All chromosomes except from the sex chromosomes
What are the sex chromosomes?
The 2 chromosome which determine the sex of an individual
Summarise autosomal recessive inheritance
- they may skip generations
- makes and females are equally affected
- all sufferers are homozygous recessive
Summarise autosomal dominant inheritance
- appear in every generation
- makes and females are equally affected
- sufferers are homozygous dominant or heterozygous
- sufferers have an affected parent
Summarise sex linked recessive
- fathers cannot pass the condition on to their son therefore male offspring must inherit the condition from their mother
- sufferers are homozygous recessive
- nom sufferers are homozygous dominant
- heterozygous females are carrier
What is pre implantation genetic diagnosis?
Pre implantation genetic diagnosis enables people with a specific inherited condition in their family to avoid passing it on to their children.
