Prenatal genetic diagnostic is a pre-natal testing procedure that gives parents-to-be, information about whether their fetus is subject to any genetic disorders. Genetic/inherited disorders are generally caused by mutations (changes) in an individual’s chromosomes or genes. Genetic disorders may include Tay–Sachs disease, cystic fibrosis, sickle cell disease etc. In most cases, both parents carrying the same gene tend to have an affected child.

The major benefit of undergoing a prenatal genetic diagnostic is that, it helps detect all conditions that may be caused by an extra chromosome and several other disorders caused due to missing or damaged chromosomes.

Several methods/technologies are used in prenatal genetic diagnostic testing. The technology is selected by the genetic counselor or obstetrician on the basis of information being sought.

DNA Tests: For instance, if the couple is a carrier of the cystic fibrosis gene, they may request for testing this specific gene mutation.

Karyotype: On taking a picture of the chromosomes and re-arranging them in order from largest to smallest, the extra, damaged or missing chromosomes can be detected. This is done through Karyotyping, and its results are prepared within 1–2 weeks after cell sampling.

Chromosome Microarray Analysis: From an entire set of chromosomes, this test helps find different types of chromosomal issues like aneuploidy (presence of abnormal number of chromosomes in a cell). It is more efficient in doing so, as compared to Karyotyping. Results of this method are prepared in 7 days.

Fluorescence In-Situ Hybridization: It is used to identify common aneuploidies involving the X and Y chromosomes and chromosomes 13, 18, and 21. Results are ready in 1–2 days, and karyotype may be further used to confirm positive test results.

Generally, the results of a prenatal genetic diagnostic test are negative (normal). However, a negative result does not rule out the possibility that the fetus has a genetic disorder. It only details that the fetus does not have the particular disorder it was tested for. If the diagnostic test result is positive (shows that the fetus has the disorder tested for), the obstetrician provides guidance about options and choices available. The disorder specialist gives information on the lifespan of the disorder, its treatment, pre-natal care, and child care associated with it. Additional testing in the form of a specialized ultrasound exam, can help find out more information about the disorder.