Drs Lee, Ridout, Walters, and Cockburn have reviewed data on 228 pregnancies occurring in women with phenylketonuria (PKU).¹ This paper provides important data which support the main findings of the Collaborative Maternal PKU Study sponsored by the National Institute of Child Health and Human Development in Bethesda, Maryland, USA.² Despite the fact that the data of Dr Lee et al are based on pregnancies occurring only in the United Kingdom, the findings verify two of the most important findings in our longitudinal, prospective study, which collected data from three different countries: the United States, Canada, and Germany. In any international study such as the latter, cultural and social differences can always interfere with statistical analyses. Therefore the fact that both studies support and concur that pregnancies in …