What disorders can amniocentesis detect?

Amniocentesis is diagnostic, so it gives definite answers rather than probabilities. What it detects depends on which tests are requested on the sample. Chromosome analysis (karyotype) counts and examines all chromosomes. This detects the trisomies NIPT screens for, and also the many chromosome abnormalities NIPT does not — including unbalanced translocations, and abnormalities of chromosomes other than 13, 18, 21, X and Y. Chromosomal microarray detects much smaller deletions and duplications, well below what a microscope can see. ACMG notes that where fetal anomalies are seen on ultrasound, invasive testing with microarray is more likely than NIPT to detect chromosomal imbalances. Targeted testing for a specific inherited condition, where one is known in your family — thalassaemia, cystic fibrosis and similar. This must be requested specifically and requires the familial gene change to be identified beforehand. Infection testing in specific circumstances. What it does not detect: Structural abnormalities — your anomaly scan covers these. Conditions with complex causes such as autism or most developmental differences. Single gene conditions that were not specifically tested for. A point worth raising before the procedure: microarray sometimes finds changes of uncertain significance, where you may be told something has been found without a clear explanation of what it means. Ask in advance how your service handles these and whether you would want to know.