After CVS or amniocentesis, parents may hear several genetic test names: karyotype, FISH, and microarray. These tests use fetal or placental cells, but they answer different questions.
Choosing the right test depends on the ultrasound finding, screening result, family history, gestational age, and what level of detail is needed.
What is karyotype?
A karyotype looks at chromosomes under a microscope. It can identify extra or missing chromosomes and larger structural changes such as translocations. It is a long-established test and remains useful when doctors need a broad chromosomal overview.
What is FISH?
FISH is a targeted test that looks for specific chromosomal changes. It can often provide quicker preliminary information for common conditions, but it does not replace a full analysis when wider testing is needed.
What is microarray?
Chromosomal microarray, also called CMA, is a higher-resolution test. It can detect smaller deletions and duplications that may not be visible on standard karyotype. It is often discussed when ultrasound shows structural abnormalities or when a more detailed chromosomal assessment is needed.
Can microarray detect everything?
No. Microarray is powerful, but it does not detect every type of genetic condition. Some single-gene disorders require other testing such as targeted gene testing or whole exome sequencing. Balanced translocations may also require karyotype interpretation.
Why counselling matters
More detailed testing can sometimes identify variants that are difficult to interpret. Before testing, parents should understand what results are possible: normal, abnormal, uncertain, or needing parental testing.
The best genetic test is not always the most advanced one. It is the test that matches the clinical question and gives information that can guide care.