The list of genetic tests in use consists of hundreds of agreed genetic tests: prenatal testing, newborn screening, predictive testing, preimplantation testing, diagnostic testing, forensic testing, carrier testing and more.
The decision to be genetic tested is based on various reasons, from confirmation of a genetic disease to evaluation of the risks of developing a specific genetic disease that has been detected to a member of family.
Since genetic tests help to determine modifications in chromosomes, genes or proteins, thus the genetic tests are classified as chromosomal tests(karyotype and fluorescent in situ hybridization analysis), gene tests and biochemical tests.
The base materials of genetic tests are usually samples of hair, skin, blood, tissues or samples of cells collected using a procedure called buccal smear.
The blood screen is performed by pricking your baby's heel and putting a few drops of blood on a special paper card. The card is allowed to dry and then is sent to the newborn screening laboratory where it is looked at for chemical abnormalities that may be a sign of a treatable medical condition. The hearing screen is done using a special machine, often while your baby is asleep.
The Save Babies Foundation has a great video out on Newborn Screening that will answer a lot of the basic questions. You can also visit their website (link below) for more in-depth q & a.