Flea bites are not usually dangerous to pregnant women. They are similar to mosquito bites and will go away on their own in several days.
Simply be careful not to scratch the bites and break the skin otherwise you run the risk of contracting an infection.
If you have contracted very many flea bites and are worried about the risk of infection, you may see your doctor to see if antibiotics are necessary, but most of the time is not needed.
Make sure to treat your pets with flea medication and treat your home with flea control products to make sure that your environment is free of fleas.