With the crown-rump-length the size of your baby and his birth date can be calculated. But what exactly is behind the SSL and why is not the baby simply being measured in total length?
At the beginning of your pregnancy, your doctor will use ultrasound to measure your baby’s crown-rump length, SSL for short, to determine its size. The crown-rump length indicates the distance between the highest point of the head and the rump of your baby between the 7th and the 13th week of pregnancy . But why does not the doctor measure the total length of your baby? This is due to the crooked position of the fetus in this developmental phase, which makes a measurement as a whole impossible.
Crown-Rump Length: Why do you measure them?
The crown rump length provides information about:
- the stage of development
- possible undesirable developments and diseases
- the expected date of birth
Determine pregnancy duration with crown-rump length
By measuring crown-rump length, your gynecologist will determine your baby’s age from the time of fertilization. This method is very accurate in the first weeks of pregnancy , because at the beginning of pregnancy, all fetuses develop the same. From about the 7th week of pregnancy , your baby grows about one millimeter a day. But do not worry if your offspring is a little smaller or bigger than the norm . After all, the moment of fertilization can not be exactly determined to the minute. If something is noticeable about your baby, your doctor will inform you.
Determine birth date with Naegele rule
With the help of Naegele’s rule and the crown-rump length your gynecologist calculates the expected date of delivery .
First day of the last period – 3 months + 1 year and 7 days = delivery date
Determine birth date by SSL measurements
The measurements of the SSL are compared with statistical values , whereby the expected date of birth can be determined. If the results of the Naegele rule and the measurement of SSL are different, the SSL calculation is preferred. The date of birth is then entered in the maternity card . However, this can be corrected again until the 12th week of pregnancy .
|Pregnancy week (SSW)||Size (in cm|
|6th week||0.4 cm|
|7th week||1.0 cm|
|8th week||1.6 cm|
|9th week||2.5 cm|
|10th week||3 cm|
|11th week||4 cm|
|12th week||5.5 cm|
|13th week||7 cm|
|14th week||8 cm|
From the 13th week of pregnancy, the biparietal head diameter, the transverse diameter of the thorax and the length of the femur (femur) are finally measured to determine the size of your baby.