DNA testing is a very powerful tool that can detect certain genetic diseases. Someday, DNA testing may be able to detect many more diseases, and even tell you if you will develop a disease down the road. Today, unless there is a specific genetic disease suspected, then usually no routine DNA tests are done at birth. Thus if you have a genetic disease that runs in the family, or if your baby exhibits certain symptoms early on, then DNA testing may be warranted. Right now, it is too expensive to be done for every new child.
With that said, there are some diseases that we do test for at birth that do not involve the child's DNA. For example there is a genetic disease called Phenylketonuria (PKU for short) that is tested for in every child. However, a sample of the child's DNA is not required to test for the disease.
I suggest that you schedule an early appointment with your child's pediatrician
just after your baby is born. The two of you can discuss what diseases are routinely tested for in everyone and which ones are only done in certain babies that are at risk of those diseases. The doctor
can determine if any testing is necessary. Good luck with your new baby.