At around seven weeks of pregnancy, it’s reasonably common for women to have their first ultrasound.
The limbs and the yolk sac, though obviously important, are not the primary means of measuring growth.
An average length of the embryo at 7 weeks is anywhere between 5mm-12mm. Obviously, every pregnancy is unique and individual factors influence the size of the embryo at this early stage, and the embryo shows development week by week.
Before the scan you will be asked to drink a lot of water and have a full bladder, as this puts the uterus in a better position to be scanned.
This can be something of an uncomfortable challenge if your sonographer has particularly long waiting times.
Other reasons to have a 7 week ultrasound are to: The embryo will be measured from the top of its head, the “crown” to its bottom or “rump”.
This is because it is the longest portion of the embryo’s body and provides an ideal measurement baseline of growth and development.
There are two routine scans in pregnancy and the first is called the 12-week scan or “dating” scan – this is because one of the things it looks at is the exact gestation, giving a better idea of your baby's estimated due date.
The dating scan is usually done at some point between 8 weeks and 14 weeks pregnant.
Further Information: Gestational age is the time measured from the first day of the woman’s last menstrual cycle to the current date. The CRL is length of your baby (top of the head to the bottom).
Please drink at least 1 pint (0.5ltr)of water prior to your scan appointment.
It can also help to diagnose abnormalities or problems, help determine the age of the pregnancy and subsequent due date as well as showing the position of the placenta in relation to the birth canal.