In early pregnancies, the actual cardiac rate is less important than its presence or absence.
The fetal pole grows at a rate of about 1 mm a day, starting at the 6th week of gestational age.
The yolk sac is first visible at 5 weeks and it is always present by 5 weeks and 4 days.
One gestational sac seen with 2 yolk sacs visible inside it Identical (monozygotic) twins.
This results from an early embryo dividing into 2 genetically identical embryos.
The embryonic pole appears adjacent to the yolk sac, soon showing cardiac activity.
Since the connecting stalk is short, the embryonic pole is found near the wall.
While your sonographer takes measurments they will explain what you are looking at.