**Core Concept**
Phenylketonuria (PKU) is a genetic disorder caused by a deficiency in the enzyme phenylalanine hydroxylase (PAH), which is necessary for the metabolism of the amino acid phenylalanine (Phe). This leads to the accumulation of phenylalanine and its metabolites in the body, causing neurotoxic effects.

**Why the Correct Answer is Right**
Children born to mothers with PKU can develop a condition known as maternal phenylketonuria (MPKU) or maternal PKU syndrome, which is caused by the transmission of phenylalanine through the placenta. This occurs because the mother's body is unable to metabolize phenylalanine properly, leading to an excess of this amino acid in her bloodstream and subsequent transfer to the fetus. The fetus is then exposed to high levels of phenylalanine, which can cause developmental delays, low birth weight, and other complications.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the condition associated with PKU.
**Option B:** This option is incorrect because it does not specifically mention the transmission of phenylalanine through the placenta.
**Option C:** This option is incorrect because it is a general statement about genetic disorders, but does not address the specific condition associated with PKU.

**Clinical Pearl / High-Yield Fact**
Mothers with PKU must follow a strict diet that limits their intake of phenylalanine to prevent the transmission of this amino acid to the fetus and to reduce the risk of maternal PKU syndrome.

**Correct Answer: D. Maternal PKU syndrome.**