What is the purpose of the reducer cushions that you find in child seats? It's true that when it comes to infants, reducer cushions are a very important part of the child restraint system. You can find both universal and specific ones; in other words, especially designed for the cot or child seat in question.
There are two ways of protecting babies in cars. One is with a Group 0 child restraint system (for infants up to 9 kg), i.e. carrycots or bassinets adapted for newborn babies. The other is to go directly for a Group 0+ CRS for up to 13 kg - i.e. baby seats - which are also known commercially as "Maxi-Cosi". Carrycots and bassinets tend to be recommended for children with special needs due to their position.
In carrycots and bassinets the baby tends to be less well secured, though there are now special devices to combat this problem. In this case, the baby travels lying down.
In contrast, in the second case the "Maxi-Cosi" lets you sit the child facing backwards for longer periods of time. In addition they usually come with reducer cushions which are more ergonomic and ensure the infant is better supported in the seat. You can find all the information you need about the different groups here.
You can now find dedicated reducer cushions (those sold for each specific child seat) as well as general ones (which can be used in any child seat and can even be designed for use in more than one type: rockers, loungers, carrycots, child car seats, etc.).
Obviously the best option will always be a reducer cushion designed specifically for your CRS, as it will be better adjusted and you will notice this in the comfort and support of your child. The generic ones will not fit in the same way as the specific ones designed by the manufacturers for each model.
These reducer cushions are often included in the child restraint system you buy for your child. They usually consist of a removable cushion whose main purpose is to ensure the correct posture and comfort of the infant. The truth is that even the smallest child seat is still too big for a newborn baby.
In addition, many of these cushions have an ergonomic head rest which helps to regulate the temperature. Usually you can remove these cushions for cleaning or when they are no longer necessary.
In most cases, these cushions are only used for the first few months of the infant's life as once they have grown they will be big enough to sit snugly in the CRS.
In this respect, we recommend that you follow the manufacturer's instructions, which will tell you from what point your child can start traveling without the reducer cushion. Normally they need it for the first 3-6 months, at which point the baby's neck starts becoming stronger. Generally speaking, from the age of around six months the child can start sitting up normally. Whatever the case, it all depends on the child's growth rate. You'll probably notice that it's time to remove the cushion when your child starts getting uncomfortable.
Finally, we would like to stress the importance of using rear-facing child seats for as long as possible, and at the very least until the child is 15 months old. Fundación MAPFRE even recommends that they are used until the child is at least four years old.
Babies should always travel in fully approved and certified baby seats. They should not be either too inclined or too flat. The ideal is an intermediate position. The reducer cushion also helps in this case to support the baby better.
We recommend you read "How to transport a new-born baby by car" and the guide "Keeping babies and children safe in cars: Child seats for vehicles" (Spanish) published by the Spanish Midwives' Association and Fundación MAPFRE.