Pregnancy and PKU

The effect on the unborn child

Pregnant mothers with PKU need to be extra careful about their Phe intake to lessen the risks of birth defects to their unborn child^28-30. Because a number of weeks can pass prior to the discovery of the pregnancy, it is especially important for a woman who is pregnant, is planning to become pregnant, or is of childbearing age to follow the Phe-restricted diet and the target Phe level that was prescribed for her by her healthcare provider. A pregnant woman should also consult her doctor and the staff at her clinic for special instructions.

Even though the child of a mother with PKU might not be born with PKU, the unborn child is still at risk of brain damage and other serious problems from exposure to the mother’s high Phe levels.

• One research study showed that women with PKU who kept their Phe levels in control during pregnancy had children with higher IQ levels than the children of women with uncontrolled PKU.²⁸
• Also, the occurrence of congenital heart disease in the children of women who closely followed their Phe-restricted diet very early in the pregnancy dropped to 1%-2% compared to 14%-17% in those women who did not control the Phe in their diets.²⁹
• Other problems in the children of women with uncontrolled Phe levels include facial deformities, microcephaly (abnormally small head size), developmental delays, and growth retardation prior to birth.³⁰
• Phe levels in the placenta can be 1.5-2 times higher than blood Phe levels.³¹