Final answer:
The correct advice for a client with epilepsy planning a pregnancy while on Phenobarbital is for her to consult her doctor because the drug is contraindicated in pregnancy and may need to be changed.
Step-by-step explanation:
A client with epilepsy prescribed Phenobarbital (Luminal) has expressed plans for pregnancy and is concerned about the safety of her medication. It is important to note that Phenobarbital is a category D drug for pregnancy, which means there is positive evidence of human fetal risk but the benefits from use in pregnant women may be acceptable despite the risk.
The nurse's correct response to this client should be: "Please talk to your doctor; this drug is contraindicated in pregnancy." This advice is crucial because the client should not make any changes to her medication regimen without consulting her healthcare provider who is equipped to evaluate the risks and benefits and may switch her to a safer alternative if necessary.