The first trimester ultrasound is performed at the 12th week of gestation. It identifies how many babies are going to be had, what their sex is (provided they are in the correct posture), if any type of anomaly can be observed, etc. In addition, the CRL is done, a very important test, sometimes unknown, and which we will delve into.
What is the CRL test?
The concept of CRL ( crown-rump length ) is an acronym in English that translates as the length of the caudal skull. This test measures “the distance between the skull and the coccyx”, as reported in the article Ultrasound in Obstetrics . The objective is that through the CRL the gestational age of the baby can be determined and thus confirm at what time the pregnancy occurred as closely as possible.
On many occasions, the date of the last period is taken into account to determine when a woman has become pregnant . However, while this is fairly objective, it is not entirely accurate. The pregnancy may have taken place a week after that date and, therefore, the calculation is wrong. The CRL test allows you to get rid of doubts.
When the date that was believed to be the gestation date does not coincide with what the CRL test is showing in the ultrasound at week 12, what it dictates will be taken into account. It is the most reliable test and, therefore, the only valid one . The measurement thanks to the CRL helps to determine as accurately as possible the date on which the pregnancy occurred .
Similarly, sometimes women trust pregnancy tests that show the weeks in which it has occurred . However, these can also give erroneous data or the estimate can be too wide, for example, between 1-2 weeks. The CRL test is the only one that will help to correctly date the baby’s age at the time of the ultrasound for proper follow-up.
How big should a baby be on ultrasound?
In the first trimester ultrasound, the baby should measure between 5-6 centimeters, according to Assisted Reproduction ORG . However, depending on the measurements offered by the CRL test, the real age of the baby will be determined. It may not be among these recommended measurements which will help date your pregnancy.
A doctor deceives several pregnant women by giving the same ultrasound to all of them for years
Knowing all this helps to establish more specifically when the delivery can occur . This information is essential so that there is adequate follow-up and the tests are adjusted to the needs of each stage that the baby will go through while in the womb.
The results of the CRL will be taken as valid, since it is a very specific test and it calculates the gestational age of the baby very well. However, it is true that there can always be a margin of error with a difference of days. Despite this, it is much more reliable than other methods to know when the pregnancy took place.