Objectives: The aims of this article are to report on a review of cases of maternal phenylketonuria in the International Maternal Phenylketonuria Collaborative Study that were initially diagnosed during or after a pregnancy, to alert health care practitioners to the possible existence of women with undiagnosed phenylketonuria whose fetuses are at risk, and to emphasize that not all adults with untreated phenylketonuria are mentally retarded.
Study design: The study was conducted through retrospective database review.
Results: Of 414 women with live-born infants, 17 fulfilled our criteria. Six had phenylketonuria diagnosed after they had produced >/=1 affected offspring, 2 had phenylketonuria diagnosed as a result of transient postnatal hyperphenylalaninemia in an offspring, and 9 had phenylketonuria diagnosed by prenatal screening. Undiagnosed maternal phenylketonuria in North America and Europe is currently estimated at 1 case/100,000 births; this rate could be higher elsewhere.
Conclusions: Physicians and midwives should consider a protocol of selective prenatal screening or case finding to detect undiagnosed phenylketonuria among their patients.