During your first ultrasound at 6 weeks and 4 days, it is possible to hear or see a heartbeat. However, it may not always be detectable at this early stage of pregnancy. The visibility of the heartbeat depends on various factors such as the position of the embryo, the quality of the ultrasound machine, and the expertise of the technician performing the scan. In some cases, you may only be able to see a flickering motion on the screen, indicating cardiac activity. It's important to keep in mind that every pregnancy is different, and not being able to detect a heartbeat at this stage does not necessarily indicate any problems. If you don't hear or see a heartbeat during this ultrasound, your healthcare provider may schedule another one in a few weeks to reassess.