Foetal measurements: how to calculate them?

Weight and length: knowing the dimensions of the foetus

Foetus

Periodic check-ups and ultrasound checks: by measuring the foetus, future mothers and fathers check the regular growth of their child and begin to know it.

Knowing the length and weight of the foetus: a common desire

During pregnancy, it is only natural for future parents to want to know if their baby is growing regularly and to want to know how it looks and its measures. Periodic visits and checks are exactly what this is all about. The weight and length measured by ultrasound are two parameters indicative of the baby’s proper development.

Calculating foetal measurements

There are two routine ultrasound scans during pregnancy. The first, called obstetric, is carried out by the end of the first trimester and allows knowing the cranio-sacral length, that is from the head to the sacrum. At this stage, it is not yet possible to measure the total length because the foetus is crouching. From the fourteenth week it is possible to perform the second ultrasound, called morphological, which allows measuring the length of the foetus from the head to the heel, as well as the humerus and femur.

If you want to know what is the foetal length without waiting for the next ultrasound, you can use an online calculator by entering the length of the femur in the calculation system, a parameter that is indicated in the last ultrasound done. The foetal length is approximately 7 times that of the femur. The foetal weight is calculated using the distance between the two ears - or biparietal diameter - and the abdominal circumference. In both cases, the results are only indicative.