A 37-year-old woman comes to the office for the follow-up. Medical therapy is significant for mild psoriasis and bipolar I disorder. The patient was diagnosed with bipolar at age 21 following a manic episode and has a history of 2 hospitalizations at age 25 and 34 for major depressive episodes. Her mood has been stable on valproate for the past 2 years; she takes no other medications. The patient recently got married and has been functioning well. She hopes to become pregnant and would like to stop her oral contraceptive in the next few months. During pregnancy, she would like to continue to take medication for bipolar disorder due to her concern about relapse.

　Which of the following is the most appropriate recommendations regarding pharmacological management in this patient?

A: Maintain valproate at the lowest ef