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Antenatal and postnatal screeningDiagnostic testing

Antenatal and postnatal screening are used to protect the health of mothers and babies. Antenatal techniques include ultrasound imaging, dating scans, blood and urine tests and diagnostic testing, such as amniocentesis, CVS and genetic screening. Postnatal screening can involve diagnostic testing such as PKU.

Part of Human BiologyPhysiology and Health

Diagnostic testing

There are two main types of diagnostic testing:

  • Amniocentesis - uses a small amount of from the amniotic sac surrounding the foetus to check for genetic disorders.
  • Chorionic Villus Sampling (CVS) - tests a sample of cells from the mother's for genetic disorders

Cells obtained from either test can be cultured to obtain sufficient cells to produce a karyotype. This can then be used to diagnose a range of conditions, such as , Turner's syndrome and Klinefelter's syndrome.

AmniocentesisCVS
When can it be carried out?14-16 weeksAs early as 8 weeks
ProcessSample of amniotic fluid is removed and culturedSample of placental cells are removed and cultured
Time taken for resultsApproximately 2 weeksImmediate karyotyping
When can it be carried out?
Amniocentesis14-16 weeks
CVSAs early as 8 weeks
Process
AmniocentesisSample of amniotic fluid is removed and cultured
CVSSample of placental cells are removed and cultured
Time taken for results
AmniocentesisApproximately 2 weeks
CVSImmediate karyotyping

There is an element of risk associated with both of these techniques.

Both increase the risk of miscarriage. CVS has an increased risk of miscarriage compared to amniocentesis. But CVS has the advantage that it can be carried out earlier in pregnancy.

Because of these risks, these tests are primarily aimed at mothers who appear to have a higher risk of having a child with a genetic disorder.

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