Hello, and I hope I can help you today. There are two possibilities of what may be going on if you do not yet see a heartbeat with your pregnancy. The first, even though you are sure of your LMP, conception can take place at a different time in your cycle than you expected. The egg can live inside you up to 72 hours after ovulation, and sperm can remain alive inside you for up to 5 days. So you actually may have conceived a week later than you thought, which means that you are only 6 weeks pregnant. It can be normal to not see a heartbeat at 6 weeks. The other possibility is that the fetus died already at 6 weeks, which is a miscarriage that has not come out yet. The way we can figure out what is going on is to check another ultrasound in a week or so. If there is no heartbeat by 7 weeks, then the diagnosis of a miscarriage is correct. So I know it is hard to be patient, but there is nothing that can be done to prevent miscarriage. One of every 10 pregnancies are miscarriages, meaning 90 percent of the time after a miscarriage women go on to have a healthy baby. I hope I was able to answer your quesion and that this information was helpful to you. Best wishes, and good luck with the pregnancy, Dr. Brown