Maternal PKU: strategies for dietary treatment and monitoring compliance

Maternal Phenylketonuria and Offspring Outcome: A Retrospective Study with a Systematic Review of the Literature

Background: Phenylketonuria (PKU) poses significant challenges for maternal and neonatal outcomes, requiring strict adherence to dietary protocols to maintain optimal maternal phenylalanine (Phe) levels during pregnancy. This study retrospectively analyzed outcomes of pregnancies in PKU-affected women and conducted a systematic review on the timing of dietary management and its impact on outcomes. Methods: This retrospective study included data from nine PKU-affected women and 14 pregnancies followed at the Regional Reference Center for Metabolic Diseases in Catania. Women were categorized based on the timing of dietary intervention: preconception (pcD), during pregnancy (pD), or never (nD). Maternal Phe levels were classified as in-target (tP+) or non-target (tP-). A systematic review of the literature was conducted using PRISMA methodology, including 77 studies reporting maternal Phe levels, dietary timing, and clinical/auxological offspring outcomes. Results: In the retrospective study, pcD and tP+ groups had significantly better neonatal outcomes, with lower rates of congenital heart disease (CHD), facial dysmorphisms, intrauterine growth restriction (IUGR), and microcephaly. Systematic review data from 1068 PKU-affected women and 2094 pregnancies revealed that pcD with tP+ resulted in the lowest rates of miscarriage (0.14%) and adverse neonatal outcomes, while tP- and nD groups showed the highest rates of CHD, microcephaly, and intellectual disability. Conclusions: Early dietary intervention, ideally preconceptionally, and achieving target maternal Phe levels are critical in reducing adverse outcomes in pregnancies of PKU-affected women. These findings emphasize the importance of metabolic control and adherence to dietary protocols in maternal PKU management.

Maternal phenylketonuria syndrome: studies in mice suggest a potential approach to a continuing problem

BackgroundUntreated phenylketonuria (PKU), one of the most common human genetic disorders, usually results in mental retardation. Although a protein-restricted artificial diet can prevent retardation, dietary compliance in adults is often poor. In pregnant PKU women, noncompliance can result in maternal PKU syndrome, where high phenylalanine (Phe) levels cause severe fetal complications. Enzyme substitution therapy using Phe ammonia lyase (PAL) corrects PKU in BTBR Phe hydroxylase (Pah^enu2) mutant mice, suggesting a potential for maternal PKU syndrome treatment in humans.MethodsWe reviewed clinical data to assess maternal PKU syndrome incidence in pregnant PKU women. We treated female PKU mice (on normal diet) with PAL, stabilizing Phe at physiological levels, and mated them to assess pregnancy outcomes.ResultsPatient records show that, unfortunately, the efficacy of diet to prevent maternal PKU syndrome has not significantly improved since the problem was first noted 40 years ago. PAL treatment of pregnant PKU mice shows that offspring of PAL-treated dams survive to adulthood, in contrast to the complete lethality seen in untreated mice, or limited survival seen in mice on a PKU diet.ConclusionPAL treatment reduced maternal PKU syndrome severity in mice and may have potential for human PKU therapy.

Maternal phenylketonuria and hyperphenylalaninemia in pregnancy: pregnancy complications and neonatal sequelae in untreated and treated pregnancies

BACKGROUND

Untreated maternal phenylketonuria or hyperphenylalaninemia may result in nonphenylketonuric offspring with neonatal sequelae, especially intellectual disability, microcephaly, and congenital heart disease (CHD). Dietary treatment to control phenylalanine concentrations can prevent these sequelae.

OBJECTIVE

We aimed to present an overview of reported pregnancy complications and neonatal sequelae of maternal phenylketonuria or hyperphenylalaninemia in untreated and treated pregnancies.

DESIGN

A MEDLINE and EMBASE search was conducted for case reports and case series that assessed maternal phenylketonuria or hyperphenylalaninemia during pregnancy. Pregnancy complications (spontaneous abortion, intrauterine-fetal-death, and preterm delivery) and neonatal sequelae [small for gestational age (SGA), microcephaly, CHD, intellectual or developmental disabilities (IDDs), and facial dysmorphism (FD)] were analyzed. Fifteen unpublished pregnancies from our clinic were added.

RESULTS

We retrieved 196 pregnancies, of which 126 pregnancies were untreated and 70 pregnancies were treated. The occurrence of pregnancy complications was not significantly different between untreated and treated pregnancies. Except for SGA, all neonatal sequelae were more frequent in untreated pregnancies. Moreover, the occurrence of SGA, microcephaly, and IDDs was significantly related to the mean phenylalanine concentration in each trimester, whereas the occurrence of FD was related only to the first trimester.

CONCLUSIONS

We present the largest cohort of untreated pregnant women with phenylketonuria or hyperphenylalaninemia since 1980. The results follow the general pattern reported by other researchers. We underline that the treatment of pregnant women with phenylketonuria or hyperphenylalaninemia is of great importance to prevent neonatal sequelae. We strongly recommend starting treatment before conception because we showed the deleterious effect of an increased mean first-trimester phenylalanine concentration on FD.

Phenylalanine blood levels and clinical outcomes in phenylketonuria: a systematic literature review and meta-analysis

Blood phenylalanine (Phe) levels provide a practical and reliable method for the diagnosis and monitoring of metabolic status in patients with phenylketonuria (PKU). To assess the reliability of blood Phe levels as a predictive biomarker of clinical outcomes in the development of treatments for PKU, a systematic literature review and meta-analysis of published trials of PKU, which included Phe level and neurological and dietary compliance outcome measures, was conducted. Within-study correlations between Phe level and intelligence quotient (IQ) were extracted from 40 studies. Significant, proportional correlations were found during critical periods (from 0 to 12 years of age) for early-treated patients with PKU (r=-0.35; 95% confidence interval [CI]: -0.44 to -0.27), where each 100 micromol/l increase in Phe predicted a 1.3- to 3.1-point reduction in IQ. Similar significant correlations were observed between IQ and mean lifetime Phe level for early-treated patients (r=0.34; 95% CI: -0.42 to -0.25), where each 100 micromol/l increase in Phe predicted a 1.9- to 4.1-point reduction in IQ. Moderate correlations were found between concurrent Phe level and IQ for early-treated patients. In conclusion, these results confirm a significant correlation between blood Phe level and IQ in patients with PKU, and support the use of Phe as a predictive biomarker for IQ in clinical trials.