Objective: To examine the outcomes of phenylketonuric (PKU) pregnancies in Western Australia including birth characteristics and cognitive and behavioural outcomes in offspring.Methods: A cross-sectional study of women and their offspring who were identified from the Western Australian Maternal PKU Program (WAMPKUP) from 1991 to 2000 was carried out. Cognitive assessments (K-BIT or Griffiths scales) were conducted on women and their children, and behavioural assessments (CBCL) were conducted on the children.Results: Thirty pregnancies by nine women were registered on the WAMPKUP between 1991 and 2000. There were 16 live births, with one preterm delivery at 32 weeks. There were no congenital abnormalities. Five of the nine mothers and their nine children (aged 18 months-10 years) participated in developmental assessments. A linear relationship was shown between lower maternal IQ scores and later attainment of metabolic control in pregnancy (r (s) = -0.828; P = 0.01). There was significant correlation between lower offspring IQ scores and later attainment of metabolic control in pregnancy (r (s) = -0.734; P = 0.02). Correlation between maternal and offspring cognitive scores was not significant. Four of nine (44%) children rated in the clinical range for behavioural problems. Compared to children with no behavioural difficulties, these children had lower cognitive abilities (P = 0.05) and maternal metabolic control during pregnancy was poor (P = 0.05).Conclusions: Poor metabolic control in pregnancy is associated with poorer cognitive outcomes and increased behavioural difficulties in offspring of mothers with PKU. The results have implications for the implementation of appropriate dietary measures before conception in PKU pregnancies, and indicate a need for the establishment of multidisciplinary teams to follow up individuals with PKU to communicate the importance of pregnancy planning, to manage PKU pregnancies, and to follow up the offspring.