Maternal phenylketonuria: A mother with the genetic disease phenylketonuria (PKU) whose high blood levels of phenylalanine (phe) are dangerous to a developing fetus. High phe is a teratogen. It can damage a baby before birth.
Women with PKU who are off the special PKU diet should restart back it, ideally prior to conception. During pregnancy they must be on the diet and have their blood phe levels carefully monitored. If the maternal PKU is not controlled, the baby (who does not have PKU) is at risk for congenital heart disease, growth retardation, microcephaly (abnormally small head), and mental retardation.