Your baby's first car seat
Most babies' first car seat is a small seat known as an infant carrier. These seats go up to 13kg or around 85cm. One of the advantages of an infant carrier is that you can carry the baby to and from the car in the car seat. Most of them can be used on a pushchair chassis and a lot of brands use the same adapters, so you can often mix and match your favourite car seat with your favourite pushchair.
Infant carriers can be installed in the car with the seat belt or on a separate ISOfix or belt fitted base. Having a base is very convenient, as it stays in the car and the seat can be clicked in and out of it in seconds.
Harnessing until four or six?
Car seats for older children come in two weight limits and will last up to either four or six years on average. A seat with a 25kg limit will last at least two years longer than one that goes up to 18kg or 105cm.
You can't predict how heavy your baby will be before it's born, but by the time they need a new car seat at around 15 months, you will know if they're big or small for their age. The average age at which a child reaches 18kg is four and a half to five, but all children are different and some can be as young as two, and others as old as six. For those on the higher percentiles it's particularly important to get a car seat that rear faces up to 25kg, because they will outgrow an 18kg seat before they're four years old and that is not old enough to move up to the next stage. We encourage everyone to keep their children in a rear facing seat up to 25kg until they no longer fit.
High back booster seats
Once the weight or height limit of your child's harnessed car seat has been reached it is time for a high back booster. These belt positioning seats can be used from 15kg, but as harnessed seats go up to 18 or 25kg, it is safer to delay using a high back booster for as long as possible.
A booster has three jobs. It needs to lift the child up so that the lap belt lies on the hips and not in the soft abdomen, it needs to position the diagonal belt correctly across the chest and shoulder, and the backrest needs to keep the child upright, even when they're asleep. So you need to choose a booster which positions the lap belt in the right place*, it must have a height adjustable headrest with a guide for the shoulder belt, and a strong supportive backrest.
A child must be AT LEAST four years old before going into a high back booster. Before the age of four they are not physically mature enough for the adult seat belt to protect them in a crash, and not mentally mature enough to sit still for the entire journey and not play with the seat belt.
If you have ISOfix points in your car, choose a booster seat that can be connected to them. Some boosters have straps with hooks and others have rigid arms. Booster seats that are connected to the car's ISOfix points are more stable in the car, won't push into the child in a crash, and you won't have to remember to strap them in when the child is not with you.
If your car doesn't have ISOfix you need to choose a lightweight high back booster. Some non-ISOfix boosters can weigh as much as 10kg which is too much weight to push into the child in a crash. A lighter seat reduces the risk of injuries.