You might want to check the guidance for vaccinations for Belize - and then run these across your doctor.
http://wwwnc.cdc.gov/travel/destinat...e.htm#vaccines
The advisory also says that Belize water can be a concern and a cause of several health issues. So watch what you drink, eating anything fresh that's washed in it (like salads), and pass on ice cubes - unless you're at a resort that swears that it uses only water filtered on site (including the kitchen). Ugh...wasn't pregnant at the time, but even being careful, I forgot about the ice cubes on a trip to Egypt and...
Oh, and if you haven't flown while pregnant, you might want to be Afrin with you on the plane. Nasal tissues swell during pregnancy and the addition of the changes in pressure as the plane makes its adjustments can be killer. I traveled through much of my second trimester and my lord that was painful til i figured out what was up and what to do.