The only suggestion I have is to get done serious advice about your m/s -- sea bands, scented tissues (the smell of chemical toilets, seafood etc might be problematic), extra thick toilet paper, things to keep you cool and hydrated, figure out whether your regular sun cream reacts differently (or if the smell is an issue) and find out what medical assistance is on board (ie: is there a Dr/nurse and an IV if you get bad?) etc.

And whether your travel insurance covers maternity stuff.

And I'm guessing you've considered already whether the trip can be postponed if you're too ill, or whether your travel insurance covers cancellation and rebooking costs?