I don't get cold sores. Have you gotten the before? Do you have herpes simplex 1? Or if you haven't been diagnosed, have you kissed someone new in the recent past? I would see your doctor and it doesn't have to be the ob/gyn. Your primary care doctor can help you. There are prescription creams for oral herpes and one over the counter cream. I would talk to your doctor before using though as I don't think there have been studies on pregnant women using the ointment. Animal studies show it to be safe in animals but you'll want doctor guidance. Generally, genital herpes is the issue with giving birth but again, not sure if there is a lot of data on oral herpes and pregnancy and birth. So, do run it by your ob/gyn also. good luck hon