How are chromosomal abnormalities in babies before birth diagnosed?
A diagnostic test such as amniocentesis or chorionic villus sampling can be recommended to confirm or exclude the presence of chromosomal anomalies. Before the test is done, it is important for the couple to consider how they might be affected if the test were to actually be positive for a chromosomal abnormality.
A procedure in which 20ml of amniotic fluid is usually extracted from the expecting mother under ultrasound guidance. Amniocentesis is performed between 15 to 18 weeks into the pregnancy. The cells are grown and processed in the laboratory for chromosomal analysis.
II. Chorionic Villus Sampling (CVS)
This procedure involves taking a small quantity of placental tissue between 9 to 12 weeks of pregnancy. The tissue is carefully processed in the laboratory and cultured for chromosomal analysis.
Fetal blood is obtained around 19 weeks of pregnancy under ultrasound guidance and cultured for chromosomal analysis.