I think it's important to tell them too! I'm sure the doctor won't judge you for it, believe me they've seen anything. And it is extremely important they know if you are on any medications as I'm sure you know they can cause problems with bubba.
Pregnancy and new parenthood are a stressful time and many patients can relapse. So the medical team can give you extra support to make sure you don't spiral into depression or mania. they can also offer you extra supportive services for when baby arrives.
Do you have a specific reason you don't want them to know? Or is it mostly for fear of being judged?