Tests and Procedures Lumbar Puncture (Spinal Tap) One of the tests that may be done on your baby is a spinal tap or lumbar puncture. This is how we tell if your child has meningitis, a serious life-threatening infection of the covering of the brain. The spinal tap is done at your baby’s bedside by one of the physicians or nurse practitioners caring for your child. It is not a dangerous procedure. A small needle, about the size of one used for IVs and blood drawing, is inserted into the lower back between the bones of the spine. About ½ to 1 teaspoon of fluid is removed and sent to the laboratory for testing. As with all tests, the spinal tap is not without some risk, such as infection or bleeding. However, these complications are extremely rare and are nearly preventable.