However it is quite normal for the fetal pole to not be visible until about 9 weeks.

A normal gestation would reveal a gestational sac, yolk sac, and fetal pole.

The fetal pole is a thickening on the margin of the yolk sac of a fetus during pregnancy.

When small, the sac cannot be distinguished from the early normal pregnancy, as there may be a yolk sac, though a fetal pole is not seen.

Products of conception may include the trophoblast, chorionic villi, gestational sac, yolk sac, and fetal pole (embryo); or later in pregnancy the fetus, umbilical cord, placenta, amniotic fluid, and amniotic membrane.

The yolk sac and embryo should be readily identified when the gestational sac reaches a certain size-a yolk sac should be seen when gestational sac is 20mm and a fetal pole should be seen when the gestational sac reaches 25mm.