A woman with PKU should be placed on what diet before conception?

• A. Strict low-phenylalanine before conception
• B. No dietary changes
• C. Diet started after conception
• D. Avoid phenylalanine only in late pregnancy

Answer: (A)

In women with PKU, what matters most for the fetus is keeping phenylalanine levels low during the early weeks of pregnancy, when organs are forming. High maternal phenylalanine can cross the placenta and cause fetal harm, including congenital anomalies, growth restriction, microcephaly, and heart defects. Because these critical developmental processes begin very early, the safe approach is to begin a strict low-phenylalanine diet before conception and maintain it through pregnancy, often with specialized medical formulas to meet nutritional needs without adding excess phenylalanine. Starting the diet after conception or delaying it until late pregnancy misses the key window of organ formation, which is why preconception dietary management is essential.