Gestational Age Week 6 (Fetal age: 4 weeks) Between 5 ½ to 6 ½ weeks, a fetal pole or even a fetal heartbeat may be detected by vaginal ultrasound. The fetal pole is the first visible sign of a developing embryo The fetal pole is a thickening on the margin of the yolk sac of a fetus during pregnancy. It is usually identified at 8 weeks with abdominal ultrasound imaging, and 6 weeks with vaginal ultrasound imaging. However it is quite normal for the fetal pole to not be visible until about 9 weeks. Hence do not lose sleep over it. Wait. If you have had bleeding from vagina, your doctor may put you on hormonal support. But if not, just awaiting for 15 days may reveal a fetal pole with a beating heart. So just wait and watch.