Many of these are metabolic disorders (often called "inborn errors of metabolism") that interfere with the body's use of nutrients to maintain healthy tissues and produce energy. Other disorders that screening can detect include problems with hormones or the blood.


In general, metabolic and other inherited disorders can hinder an infant's normal physical and mental development in a variety of ways. And parents can pass along the gene for a certain disorder without even knowing that they're carriers.


With a simple blood test, doctors often can tell whether newborns have certain conditions that eventually could cause problems. Although these conditions are considered rare and most babies are given a clean bill of health, early diagnosis and proper treatment can make the difference between lifelong impairment and healthy development.