An untreated woman with classic phenylketonuria becomes pregnant. Her fetus is genotypically normal. Which fetal complication is directly attributable to maternal hyperphenylalaninemia crossing the placenta?

• A Congenital cataracts and sensorineural deafness
• B Neonatal hyperbilirubinemia from glucuronyl transferase immaturity
• C Bilateral renal agenesis and polyhydramnios
• D Microcephaly, congenital heart disease, and intellectual disability ✓

Explanation

Maternal PKU syndrome occurs when maternal phenylalanine above roughly 600 micromol/L crosses the placenta and acts as a teratogen, producing microcephaly, congenital heart defects, low birth weight, and intellectual disability in an unaffected fetus. Prevention demands strict dietary control before conception and throughout pregnancy. Option A describes congenital rubella or galactosemia sequelae, not phenylalanine embryotoxicity.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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