Never heard about 'pre' cochlear hydrops. Do you feel ear fullness? If you have hydrops, you should have dizziness and/or hearing fluctuation and/or ear pain-fullness...
If I was you, I would definitely try a low dose of diuretics. I would maybe also try a low dose of SERC. I read it helped many people with hydrops/Meniere. I don't see how it could affect your baby. It didn't help me personally, but my diagnosis is still unknown exactly... I would start with low doses and see. Maybe add more within a few weeks.
As general rules: cut on salt, sugar, coffee and chocolate. Avoid alcohol completely. Since Meniere and other ear problems seems to be virus related (as of today's), you could also ask for antiviral meds type, such as acyclovir (brand name Valtrex). Woman with genital herpes sometimes got it prescribed in a suppressive way when they are pregnant, so I don't think it could harm the baby. I've also been told to cut on all kind of nuts, peanuts, almonds, etc. to help with viruses.