Well hon, I am not pregnant yet, but I might be able to shed some light on this. I cough up blood quite frequently (every 3-4 mos) and usually if I have a spell that long (10 min or more) it means that I may need to have the blood vessels in my lungs cauterized. I don't know if I am saying this the technical way but, when you have scar tissue in your lungs your blood vessels duplicate to try and heal the scar tissue. Sometimes they burst out of no where. You literally could be walking down the street or sitting down and you will start coughing up a good amount of blood and it is hard to stop. When this happens I drink cold water to get it to stop. This happened to me at a sugarland concert! I have had two cauterization procedures. They are not as bad as you think and are usually out patient. It corrects the problem for about 5 years. I can understand your concern because you are pregnant and coughing up blood is never fun. My doctor made me have these surgeries to prevent me from possibly asperating on the blood. Some people have choked but I think it is pretty rare. You could just have a lung infection but if you weren't really ill or coughing a lot then this may be your issue.