BACKGROUND Maternal phenylketonuria (PKU) is an embryo-fetal syndrome including microcephaly and various organ (mainly cardiac) defects. It is caused by the toxicity of high phenylalanine levels in the blood from mothers with PKU who usually are off diet as adults. Maternal PKU is prevented by strict dietary phenylalanine restriction during pregnancy. PATIENTS AND RESULTS In Austria since 1967, 59 female PKU patients were born who at present time are between 16-32 years of age. We report on 11 pregnancies from 6 women with PKU who asked for dietary treatment during pregnancy. 5 newborns from 5 pregnancies with good dietary control (preconceptionally and during the entire period of pregnancy) were normally developed during an up to 5 year-somatic and neurodevelopmental follow up. In one pregnancy dietary control was achieved only after the first 5 weeks of pregnancy. the respective newborn had congenital heart disease, but otherwise was developed normally. 3 newborns from 1 mother who was not able to achieve dietary control during the entire period of pregnancy, had typical symptoms of phenylalanine embryofetopathy. 2 pregnancies were terminated by spontaneous abortion despite preconceptional dietary control. CONCLUSION Preconceptional dietary balance and low blood phenylalanine levels are important for normal embryo-fetal development. The dietary management of pregnant PKU women should be carried out in specialized metabolic centers with experience in the treatment of PKU in close cooperation with the obstetrician.