As its name suggests, the dating ultrasound is used to date the beginning of pregnancy. But it is often confused with the first trimester ultrasound. We take stock of the dating echo with Dr Françoise Boussion and Dr Emmanuelle Barrali Golstenne, gynecological-obstetrical sonographers.
Many people think that dating ultrasound corresponds to that which is carried out between 12 and 13 weeks of amenorrhea, better known under the name first trimester ultrasound. A confusion that has the gift of annoying specialists. In reality, the first trimester ultrasound is done between 11 and 13.5 weeks of amenorrhea while the dating ultrasound takes place at the very beginning of pregnancy. When to do it? What is the dating echo used for? Here is the advice of Dr Françoise Boussion and Dr Emmanuelle Barrali Golstenne, gyneco-obstetrical sonographers.
What is dating ultrasound?
Idating ultrasound is a very small ultrasound that is performed to specify the date of the beginning of pregnancy. “It can be useful in women with irregular cycles to dating the start of pregnancy in order to be sure to carry out first trimester ultrasound right in time. This examination is crucial since it allows in particular the screening of trisomy 21. However, if it is too early or too late, we will not be able to do it.“, says Dr. Emmanuelle Barrali Golstenne.
“Dating ultrasound can be useful in women with irregular cycles to date the beginning of pregnancy in order to be sure to perform the so-called first trimester ultrasound in due time”.
When to do a dating ultrasound?
Dating ultrasound can be performed as soon as we see an egg sac in the uterus, i.e. between 5 and 9 weeks of amenorrhea (i.e. between 3 and 7 weeks of pregnancy). “What you need to know is that this ultrasound is often wrongly prescribed. In theory, it should only be done in specific cases, namely if the patient had no periods, if she had very irregular periods, if she had unexplained bleeding, if she had a history of multiple pregnancy or ectopic pregnancy“, makes a point of specifying Dr. Françoise Boussion.
The embryo is not visible until five and a half weeks. Before, we only see the pregnancy bag. When performed between 7 and 8 weeks, the embryo measures 10 to 15 millimeters, we do not even see the limbs or the head. “The only thing that we can detect at this stage are terminated pregnancies, ectopic pregnancies and twin pregnancies. Often, it is so small that one is obliged to pass by endovaginal way. It takes two minutes, it goes very fast“, adds Dr Françoise Boussion.
Is the dating ultrasound mandatory?
Since the dating ultrasound is not indicated, it must imperatively be justified by an order. “Most of the time, it is the gynecologist who will follow the patient during her pregnancy who does the dating ultrasound in his office with his own device, observes Dr Françoise Boussion.
How much does a dating ultrasound cost?
“The ultrasound is listed but generally, gynecologists count it as a normal consultation and not the ultrasound act so it is reimbursed“.
What is the difference with the 1st trimester ultrasound?
The first trimester ultrasound is one of three recommended — but not required — ultrasounds during pregnancy. “It is essential since it provides information of the utmost importance. At this stage, the organogenesis is complete, so we will be able to perform the cranio-caudal measurement (head-buttocks) which allows us to refine the dating if necessary.emphasizes Dr. Emmanuelle Barrali Golstenne. There is already a mini morphology of the brain, we can see the eyes, the ears, a fairly clear profile, details of the heart, the four limbs, the fingers, the feet. First trimester ultrasound also assesses the risk of chromosomal abnormalitiesand more particularly that of trisomy 21 thanks to the measurement of the nuchal translucency, that is to say the thickness of the tissues of the neck of the fetus“.