You may think your child's first test will come in school, but it will actually happen before leaving the hospital's newborn unit.

Early screening tests for babies can find problems before symptoms arise, prompting early treatment. "These screenings can sometimes mean the difference between a healthy start in life and disability, or even death, for a baby," says Jennifer L. Howse, M.D., president of the March of Dimes. Most screenings involve a blood test. The sample often goes to a state laboratory; your baby's doctor gets the results.

Newborn screening requirements vary by state. The March of Dimes, which wants to expand screenings in many states, recommends checking for:

• Biotinidase deficiency: an enzyme deficiency that can result in physical and mental problems.
• Congenital adrenal hyperplasia: CAH is characterized by an imbalance in hormones; some are higher than normal, some are lower.
• Congenital hypothyroidism: a hormone disorder that can slow brain development and growth.
• Cystic fibrosis: a genetic disorder that affects the lungs and digestive system.
• Galactosemia: an inability to change galactose, a sugar in milk, into glucose (blood sugar), sometimes causing physical or mental problems.
• Homocystinuria: an amino acid disorder that can result in mental or physical problems.
• Maple syrup urine disease: an amino acid disorder that can result in physical problems.
• Medium chain acyl-CoA dehydrogenase deficiency: a disorder in which babies can't burn fat when they run out of glucose. It can cause physical problems.
• Phenylketonuria: a disorder in which the amino acid phenylalanine builds up in the blood, causing mental problems.
• Sickle cell anemia: a hereditary blood disease more common in African Americans.
• Hearing loss: a microphone or earphone is placed in the baby's ear to test for hearing loss. If it's found, use of a hearing aid during the baby's first six months can help head off language problems.

Dr. Howse says the March of Dimes supports these tests because the disorders, though not all common, are treatable.

To learn which tests your state performs, ask your doctor or go to the National Newborn Screening and Genetics Resource Center. Talk with your doctor about the need for screenings that your state doesn't require. The doctor might suggest other tests, too, based on your family history.