do i need to throw out my old car seat and get an i-Size one?
Hold that thought. Although i-Size is the brand new European standard, it's not replacing the old regulations. The two are running alongside each other, and seats tested under the old standard are still safe to use. One day the old regulations will be phased out, as the idea is for all car seats to meet the stricter safety standards of R129. You can find out which regulations your car seat has been tested under by checking the letters and numbers on the side.
why is travelling backwards safer?
Under the old regulations children could switch to a forward-facing car seat at nine months, but it's actually safer to keep them in a rear-facing car seat for as long as possible. Babies are built differently to adults, and their little bones are really fragile. They've also got bigger heads than grown-ups. No, we're not talking about ego – their proportions are different when they're small. If they're facing forward and you need to brake hard, the force of being thrust forward could do significant damage to their neck and spine.
why does height give a better idea of fit?
Aside from regulations based on your child's height, another reason to choose a height-based car seat that it's easier for you, the parents. It's easier to take your baby's height with a tape measure than it is to weigh them. You can also tell if they're starting to grow out of it. Another reason why height is better is that children grow at different rates. Some children have growth spurts earlier than others, but they might weigh the same as a child who's much shorter.