Phenylketonuria during pregnancy: how we managed four women

Background Maternal Phenylketonuria (mPKU) is a pathologic condition caused by elevated and prolonged intrauterine phenylalanine (Phe) levels which can lead to congenital abnormalities and mental retardation. Management of PKU during pregnancy can be challenging as protein substitutes – which are necessary for a balanced diet – may exacerbate nausea, vomiting, and gastrointestinal symptoms typical of this period. In this context, we report four cases of PKU women focusing on the complications and their management over the conception and pregnancy period.

Case study One woman was diagnosed with PKU in adulthood after repeated miscarriages and the other three by newborn screening. As all patients intended to or occurred to become pregnant, they were administered with prolonged-release amino acid supplementation, and they were recommended to follow a strict diet. Phenylalanine plasma concentration, adherence to diet, and occurrence of adverse events were closely monitored for the entire duration of pregnancy.

Results

All patients achieved optimal metabolic control with safe levels of blood phenylalanine concentration before pregnancy (mean Phe concentration 6 months prior to conception of 264.0, 144.0, 334.7, and 258.0 µmol/L for case 1, 2, 3, and 4, respectively). During gestation, all patients manifested gastrointestinal symptoms such as nausea, gastrointestinal reflux, and abdominal bloating which resolved changing protein substitute, extending the time window between different meals and amino acid mixtures intake or spontaneously. All fetuses grew within the normal ranges and the patient were able to continue their pregnancies without experiencing further complications.

Conclusions In our experience, the use of prolonged-release amino acid formulations was well tolerated by patients, allowing optimal metabolic control, reduction of gastrointestinal discomfort, and fetal growth within normal ranges.