单选题 The nurse is caring for a woman with phenylketonuria who wants to start a family. Which of the following guidelines should the nurse provide the woman?
A. Follow a low-phenylalanine diet before trying to conceive.
B. A low-phenylalanine diet is necessary only during the first trimester.
C. Begin a low-phenylalanine diet when pregnancy is confirmed.
D. Dietary restrictions won't be necessary.

【正确答案】 A

【答案解析】A woman with phenylketonuria should begin a low-phenylalanine diet before she tries to conceive. This will reduce the risk of giving birth to a baby with microcephaly, mental retardation, and low birth weight. The low-phenylalanine diet must be continued throughout pregnancy and during breast-feeding. Starting a low-phenylalanine diet after conception increases the risk of physical and mental disabilities to the fetus.