The newborn screen tests for things like hormonal, metabolic, and genetic conditions. Essentially, right after delivery, the baby is changing fast. There are a lot of hormone changes and electrolyte changes, etc., and all this can affect the screen. So the state, which requires the screen, doesn’t even accept one that has been done before 24 hours. Doing it early means that it must be repeated, and some outpatient pediatric practices aren’t used to or equipped to send a newborn screen.