Why do hospitals now test all newborns for PKU?

PKUs, Newborn screens, test infants for genetic disorders which may be treated if caught early...the pku has 26 tests including, thyroid, sickle cell, downsyndrome, and many other disorders which may be passed by mom or dad...in Texas, this is a mandated test...parents may not like their baby being poked on the heel, but it is a very important test...