Diagnostic testing
There are two main types of diagnostic testing:
- Amniocentesis - uses a small amount of amniotic fluidLiquid that protects the fetus in the uterus. 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 placentaThe organ in the uterus of pregnant mammals that allows the transfer of nutrients and waste products between the mother and the fetus through the umbilical cord. 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 Down's syndromeA chromosomal condition caused by the presence of a third copy chromosome 21., Turner's syndrome and Klinefelter's syndrome.
| Amniocentesis | CVS | |
| When can it be carried out? | 14-16 weeks | As early as 8 weeks |
| Process | Sample of amniotic fluid is removed and cultured | Sample of placental cells are removed and cultured |
| Time taken for results | Approximately 2 weeks | Immediate karyotyping |
| When can it be carried out? | |
| Amniocentesis | 14-16 weeks |
| CVS | As early as 8 weeks |
| Process | |
| Amniocentesis | Sample of amniotic fluid is removed and cultured |
| CVS | Sample of placental cells are removed and cultured |
| Time taken for results | |
| Amniocentesis | Approximately 2 weeks |
| CVS | Immediate 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.
