She is unsure what to do. For the last six months, she's been euthymic. I would appreciate any thoughts you may have. This is a bit more complicated than the average question that come from a patient when we are covering for a colleague. Since at present there is no evidence of a rebound loss of mood control if divalproex is stopped abruptly, I would stop, not taper.
Serum level is also a factor.
She and you need to decide whether to add prophylactically another mood stabilizer, selecting one thought not to have a risk of teratogenicity. There is no clear guideline on this question. Given her apparent stability, I would suggest close observation, with attention to good bipolar hygiene, e.g, adequate, regular sleep, no alcohol. Then, if any symptoms develop, the medication selected could be targeted toward the specific symptoms that she is experiencing. The circumstances of her becoming pregnant are important in counseling her regarding her decision to continue the pregnancy.