I've never read anywhere where there is an inherent problem, you should be careful with the chemicals you use in your tank (course you should do this pregnant or not) and use precautions when handling your critters...your a nurse...steal some powderfree latex gloves for working in the tank
Also there is a bacteria that can be found in aquaria (rarely) that is communicable to humans, it is fish tuberculosis Mycobacterium Marinum, again though this is something you should always keep in mind.