This observational study aims to recruit females, aged 16 years and over, with phenylketonuria (PKU) or hyperphenylalaninemia (hyperphe) following dietary management advice pre-conception and/or during pregnancy, who are willing to take PKU sphere as part of their dietarty management.

The aim of this study is to observe dietary management and metabolic control in women taking PKU sphere pre-conceptually and/or during pregnancy. To do this the following data points will be captured:

• Blood spot phenylalanine and tyrosine levels to measure metabolic control
• Changes to dietary management and any adaptations arising from incorporating PKU Sphere
• Compliance/adherence of patients to their recommended amount of protein substitute prescription.
• Tolerance of PKU sphere with respect to gastrointestinal (GI) symptoms and pregnancy associated nausea and vomiting.
• Acceptability of concurrent protein substitute(s) (if applicable).
• Nutritional status and weight management.
• Routine standard of care data on the final pregnancy outcome and postpartum.

Inclusion Criteria:

• Diagnosis of phenylketonuria (PKU) or hyperphenylalaninemia (hyperphe) which requires dietary management during pre-conception and/or pregnancy.
• Aged 16 years and above.
• Following dietary management advice pre-conceptually and/or during pregnancy, aiming for phenylalanine levels of 120-250µmol/L.
• Prior positive PKU sphere taste test completed as part of routine care.
• Chosen to take part or full requirement of protein substitute as PKU sphere pre-conceptually and/or during pregnancy.
• Willingly given, written, informed consent from patient.
• Participant is, in the opinion of the investigator, able to participate and can comply with the study protocol.

Exclusion Criteria:

• Conception of pregnancy without commencement of phe-restricted diet and blood phenylalanine not maintained within target range by 10 weeks' gestation.
• Patients with known soya, milk or fish allergies / intolerance.
• Intake of pegvaliase or large neutral amino acids within 30 days prior to screening visit.
• Patients who are currently participating in, plan to participate in, or have participated in an interventional investigational drug, food or medical device trial within 30 days prior to screening visit.

Maternal and preconception females, aged 16 years onwards with phenylketonuria (PKU) requiring dietary management with protein substitutes.