All About Karyotype Test
Know all about the Karyotype Tests: what it is, its process, risks, the ethics and the alternatives to make the knowledgeable decision.
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Last updated on 3rd Jul, 2025
A karyotype test is a specialised medical test that examines the number and structure of chromosomes in human cells. This diagnostics process provides a detailed picture of chromosomal arrangements to identify genetic abnormalities or conditions linked to chromosomal changes. It allows a doctor to study the possibility of genetic disorders, miscarriages, and particular types of cancer in a foetus. The importance of this test lies in the fact that it offers insights that guide medical decisions and personalised treatment plans.
Basics of Chromosomes
Chromosomes are thread-like structures found in the nuclear of every human cell. They carry genetic information in the form of DNA. A healthy human being will have 46 chromosomes, organised in 22 pairs of autosomes and 2 pairs of sex chromosomes. These chromosomes play a vital role in determining an individual’s physical and genetic traits.
A normal and healthy baby will have perfectly structured chromosomes with no extra, missing, or rearranged parts, ensuring proper cell function and development. However, if there are any anomalies in this arrangement, the baby will suffer from different genetic disorders, like Down syndrome, Turner syndrome, etc.
Indications for a Karyotype Test
There are a few vital circumstances under which the doctor makes it imperative to conduct a Karyotype test. Such occasions are –
If the mother’s age is 35 and above
If the unborn child has a sibling with a chromosome issue
If any of the parent has anything uncommon in their chromosome
If the mother has had more than one miscarriage
If the mother has borne a stillborn baby before
Typically, this test is conducted during the prenatal stage when the doctors suspect a chromosome mismatch. It is done after 10 to 12 weeks into the pregnancy. Here, the doctors remove some cells for further investigation. This test successfully shows if the baby has any chromosome issues.
The Procedure of the Karyotype Test
The process of the karyotype test starts with a sample collection, which is conducted using the following methods –
Chorionic Villus Sampling (CVS): In this procedure, the doctor uses a long needle to remove tissues from the chorionic villi, commonly known as the placenta. Since this is a very risky test, it is not advisable to conduct it unless the doctor feels there is a strong chance of the foetus having a chromosome issue.
Amniocentesis: Here, the doctor collects a specimen from the mother's amniotic sac and sends it for further investigation. This test is usually conducted during the 15 to 20-week periods of pregnancy.
Laboratory Analysis Process
After collecting the sample, the cells are cultured in a laboratory to observe division, as chromosomes are most visible during cell division. The cells are then stained and examined under a high-powered microscope to create a visual representation of the chromosomes, known as a karyogram.
After that, the laboratory specialist arranges the chromosomes in pairs, evaluates their number and structure, and identifies any abnormalities. This detailed analysis provides critical insights into genetic conditions, which help in diagnosis and future treatment planning.
Interpretation of Karyotype Results
A normal karyotype test result gives a straightforward answer. When the chromosome count is normal, i.e. 46 chromosomes, organised in 22 pairs of autosome and 2 pairs of sex chromosomes, the results are regarded as normal. It means the foetus is healthy and the doctor will not prescribe any following tests.
However, if there is a mismatch or any problem, the doctor will prescribe certain advanced tests to determine the root cause. Some of the common abnormalities observed are –
Down Syndrome: This syndrome occurs when the test results determine that the baby has an extra copy of chromosome 21. This later hampers the learning abilities and the appearance of the baby.
Edwards Syndrome: This syndrome occurs when test results determine that the baby has an extra copy of Chromosome 18. In this case, they have multiple health problems and don’t usually live for more than a year.
Klinefelter Syndrome: Observed in male babies born with an extra X chromosome. They are mostly unable to produce babies and hit puberty much later than the ideal age.
Patau Syndrome: This syndrome occurs when the baby has an extra copy of Chromosome 13. Here, the babies have cardiac problems and, are born with mental disability and do not survive more than a year.
Turner Syndrome: This happens to a female baby when she misses out or is born with a damaged chromosome X. This might cause cardiac issues, neck problems and short stature.
Limitations and Risks of Karyotype Tests
While Karyotype Tests come out with helpful results, it is an extremely risky test to conduct. There are high chances of a miscarriage while these tests are carried out. It has also been found that 1 out of 200 women suffered a miscarriage after this test had been conducted. After a biopsy or a bone marrow aspiration, there are very high chances of infection and heavy bleeding. This is why utmost precautions must be taken, and doctors only advise this test when they are certain of genetic abnormalities.
Alternatives to the Karyotype Test
While the karyotype test is a valuable diagnostic option, advancements in genetic technology have introduced alternative methods that offer more detailed and comprehensive analyses. These are –
Competitive Genomic Hybridisation (CGH)
CGH detects the copy number variation in chromosomes, like deletion or duplication, without performing the cell culture. This is a way in which the full overview of chromosomal gains and losses are incurred throughout the tumour genome. Additionally, CGH is particularly useful for detecting micro-deletions or duplications that are too small to be observed in a traditional karyotype test.
Next-Generation Sequencing (NGS)
NGH is one of the latest methods that offers a clear understanding or picture of the entire genome. Unlike karyotype testing, which focuses on chromosomal structures, NGS examines the sequence of DNA, identifying even the smallest genetic mutations or variations. This test is ideal for diagnosing complex genetic disorders, rare diseases, or conditions that involve single-gene mutations.
Clinical Applications of the Karyotype Tests
Karyotype tests are used to determine the genetic inabilities of an unborn foetus. It also helps in treating some other conditions like –
Genetic Inabilities: This helps determine chromosome mismatch and diseases like Down syndrome, Turner syndrome, and Klinefelter syndrome.
Male Fertility: This helps in determining genetic issues where a male might be having problems with impotency and infertility.
Cancer and Blood Issues: This test helps determine cancerous cells in the body and determines leukaemia, lymphoma, and multiple myeloma.
Ethics Related To Karyotype Test
The main ethical conservation associated with this test is consent. Before this test is carried out, it is imperative to divulge details of the test to the screened individual. Also, following the test and the results, the doctors and the clinic need to maintain confidentiality. And no third party should be informed without the permission of the screened individual.
Final Thoughts
Karyotype tests help determine any mismatch of chromosomes in an unborn foetus. This helps doctors to recognise if the child will be born with any fatal condition. Other than this, various other diseases are determined through this test, like cancer, infertility among males, and also blood-related issues. Although this test might have high-risk factors associated with it, patients need to be extra cautious when opting for it. Therefore, understanding this process in detail and its risks and alternatives is key to making a knowledgeable decision.
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