KA4 Antenatal and Postnatal screening Flashcards
What is Antenatal screening?
A variety of techniques can be used to monitor the health of the mother and developing foetus. Antenatal screening identifies the risk of disorder so that further tests and a prenatal diagnosis can be offered.
What are the 2 types of routine scans women have using ultra sound technology?
A dating scan
A anomaly scan
What is a dating scan?
They happen at 8-14 weeks
They determine the stage of pregnancy and the due date
Dating scans are used with tests for marker chemicals which vary during pregnancy
What is an anomaly scan?
They happen at 18-20 weeks
They may detect serious physical abnormalities in the foetus
What are biochemical tests (screening) ?
Routine blood and urine tests are carried out throughout pregnancy to monitor the concentrations of MARKER CHEMICALS. These marker chemicals may indicate a medical condition with an unborn foetus.
What happens if you measure a chemical at the wrong time?
Measuring a chemical at the wrong time could lead to a false positive result. An atypical chemical concentration can lead to diagnostic testing to determine if the foetus has a medical condition.
What are diagnostic tests and when are they offered?
Further diagnostic tests which will provide definitive results are offered to pregnant women when:
Routine screening has highlighted a problem
The individual is high risk (over 35)
There is a history of harmful genetic disorder in the mothers family
What is Amniocentesis?
Cells from amniocentesis can be used to make a karyotype which can detect chromosomal abnormalities. Cells are removed from the amniotic fluid in the sac.
What is Chorionic villus sampling (CVS)?
CVS from the PLACENTA can be carried out earlier in pregnancy than amniocentesis, although it has a higher risk of miscarriage.
What is the difference between screening and diagnostic?
Screening tests identify the possibility of a disorder whereas diagnostic tests identify the presence of a disorder very precisely.
Why is there a risk analysis in deciding to proceed with diagnostic testing?
Diagnostic tests are invasive and may cause damage to the foetus or trigger a miscarriage
What is a karyotype?
A karyotype shows an individuals chromosomes arranged as homologous pairs.
What are the sex chromosomes?
the X and Y chromosomes (pair 23)
Women XX
Male XY
What is sickle cell anaemia an example of?
Autosomal incomplete dominance
SS- Sickle cell anaemia
AA- Normal red blood cells
SA- Sickle cell trait (two dominant alleles)
Heterozygous individuals have a milder condition of the disease.
Why do the Y chromosomes not have letter in sex linked crosses?
The X chromosome is larger than the Y so it can carry more genes which are not on the Y, these genes are said to be sex linked
