Parents are always eager to start using a larger car seat too soon, often before children are 9/10 months old (less than 10 kg) because this is when they start kicking the back of the front seat. Don't! Babies should only be moved to a larger seat when they are about to reach the maximum weight or height for which the seat is recommended, when the harness is too far below shoulder-height, or when their head is higher than the top of the backrest. So, even if they can kick the front seat or don’t have much leg space, don’t compromise their safety. If necessary, remove their shoes so that they have more space and can travel comfortably. As is the case with several national and international bodies, APSI (Portuguese Association for the Promotion of Child Safety) recommends that children travel in rear-facing car seats for as long as possible - ideally until they are 4 years old, but at least until they are 2. Comparatively to their total body weight, children's heads are quite heavy and large (approximately 25% compared to 6% for adults) until they are 4 years old, which is why rear-facing seats are safer in the event of an accident. There are certified car seats on the market for children up to 18 Kg or 25 Kg (R44) or up to 105 cm (R129) which allow for rear-facing transport until very late. Once they are 3 or 4 years old, or weigh 15 Kg, they can then be moved to a booster seat with backrest. These can usually be height-adjusted so that the safety belt holds both the child and the seat together as one.