This really depends on how far along you are in your pregnancy, where the placenta is located in relation to where the baby is situated, and many other variables. If you try to locate the baby’s heartbeat before 7-8 weeks, it is next to impossible to locate it using the monitor. This is because the baby is still very small, and the heartbeat is very faint to detect. So, we recommend starting at about 14-16 weeks, so the baby has grown a little, and the heartbeat is also stronger. The first time you try, and cannot hear the baby’s heartbeat, don’t be discouraged. Try again in a couple of days.