Usually the embryonic sac is located first in ultrasonography. If it is done abdominally, it takes about 8 weeks from the date of last menstrual period to show the foetal pole. However, with vaginal route, it may be visualized about 2 weeks earlier; i.e. 6 weeks from last menstrual period. In some cases, particularly depending upon the position of the uterus and the site of implantation of the embryo, foetal pole may not be visualized up till 9 weeks also. The question in concern where the foetal pole is not visualized is whether there is any living embryo inside the gestational sac or not. The simple guideline for this is that if the embryo inside is not living or absent, what we doctors call it a blighted ovum, then the edges of the sac look corrugated. In a normal pregnancy, they are smooth. Usually if it is a blighted ovum, the pregnancy terminates by itself, occasionally requiring assistance in completing the abortion.