How is it actually?

Moms (and dads) who are new to the babywearing world often get lost in a jumble of different information.

They are often confused about when and for how long a carrier can be used. Why is a baby carrier that says "from 3.5kg to 20kg" only suitable from 4 months to a maximum of a year, according to other mums? After all, 3.5 kg is for newborns and 20 kg is for 4-year-olds, so why shouldn't it be for the whole carrying period...?

The answer is very simple... humanly speaking, because the norm.

In the former standard for cloth carriers (not distinguishing between a reinforced or unreinforced back support, but a carrier vs a loom with a fixed structure) EN 13209-2:2005, the carrier was tested with a test ball of a minimum weight of 3.5kg with a carrying capacity automatically up to 15kg or the maximum weight stated by the manufacturer. The standard itself then stipulated that the minimum and maximum test weight must be stated for the product. It was then purely up to the manufacturer whether to write a realistic period of use for the stretcher. That is why with older KiBi´s you can see information that it is from 3,5 kg to 20 kg and at the same time it is recommended from 4-6 months to about 3 years, depending on the size of the child.

The newer EN 13209-2:2015 standard already stipulates that the product should carry a label indicating what minimum age it is suitable for and the maximum tested load capacity. Thus, in the case of the KiBi baby carrier, 4-6 months up to 20 kg (still with the addition of up to approx. 3 years, depending on the size of the child, because every child is different).

However, it is still not mandatory to inform about the total realistic period of use from-to and therefore it is purely up to the manufacturer whether to provide this information.

Similarly, there is as yet no official standard to determine which baby carrier can be described as ergonomic.

There are basically 3 main principles for an ergonomic carrier:

It does not have a reinforced/fixed backrest - with a fixed backrest, it is not possible to achieve the correct seating and rounding of the back that is essential for small babies - small babies do not yet have strengthened muscles.
 

It has enough fabric to support the legs from knee to knee - the fabric of the back support should extend into the knee sockets so that the legs do not hang but are in the "M position" (knees higher than buttocks), which is good for healthy hip development. (Similarly, the height of the backrest should also provide support.)
 

It is not designed to be worn facing out, with the back to the person carrying the baby - in this position the baby's back is arched, the baby is basically hanging by the crotch (especially if there is not enough of fabric to support the legs) + it receives a lot of external stimuli from which it is not protected and may suffer psychologically.

Unfortunately, the norms are still not yet in tune with reality...