Glad your trip worked out. I had two friends visit me in Istanbul and both were four and five months pregnant. They really enjoyed Istanbul and had no problems in the city except for when they took a taxi off the street - as then (and still now) many taxis don't offer seat belts, or they push the plug under the seat so they're difficult to use (as seat belts are considered a discomfort for local passengers!). Being pregnant and safety conscious, they asked one taxi man to slow down, but he laughed and told them to just "hang on!" instead. Moral of the story is if pregnant, I would recommend to take public transport or hire a private car, or if you have to get a taxi, have one called by your hotel reception so that they are reputable.