Why is the dating exam ordered?
At this ultrasound there is an opportunity to confirm that there is a pregnancy located within the uterus and observe the other pelvic anatomy. Depending on the timing, if this exam is done around 8 weeks gestational age, there is also the ability to identify and measure the embryo, and document the heart motion. This is the time to quantify the size of the pregnancy and the timeline. If the embryo measures greater than 10mm in the crown-rump-length (CRL) then it is possible to officially “date” the pregnancy and offer the expected due date (EDD). The accepted standard of practice according to the SOGC is to use the first trimester dating scan to establish the EDD, as this is more reliable and accurate then the last menstrual period.
It is useful to note that if the dating ultrasound is booked too early and the embryo does not meet the criteria of being equal to, or greater than, 10 mm in CRL than no EDD will be provided, and no official dates will be given. It is also important to remember that coming too early in the pregnancy also means that there may be no definitive signs of heart motion yet, or a distinguishable embryo. This can be normal, as it may just be too early, and time needs to pass to allow for the growth and progression of the pregnancy.
In this case you may be recommended to have a follow-up ultrasound in 10-14 days, but this will be at the discretion of the referring physician.
What can you expect at your dating ultrasound?
When you arrive for your appointment every effort will be made to see you in a timely manner, we are very aware that you have filled your bladder in preparation for this exam. Thank you. We do not want you to wait with a full bladder either!
Once the technologist has called you in from the waiting area and confirmed your identity, you will be invited to lay down on the cushioned table. At this point you may indicate whether you would like the patient viewing screen on so that you can see along with the technologist.
Depending on how far along you are in your pregnancy and how well the technologist is able to see with the ultrasound, there may be an indication to offer an endovaginal approach to better visualize your uterus. This is only done with your consent and at your level of comfort. If you would prefer NOT to have this done, that is no problem at all!
**If you are over 8 weeks gestational age you will very likely be able to see the cardiac motion, and get to find out the heart rate.
You will also receive a picture to take home as a keepsake, and a card with your due date.*