If you have chosen to put your baby in an infant car seat, you need to switch them over at the right time. They will eventually get to the point when they have outgrown the highest height and weight of the infant car seat set by the manufacturer. Generally, this comes between nine and 18 months, but check the guidelines to be certain. Babies should be rear-facing in the back seat until the age of two, as research has shown that they are much less likely to be severely or fatally injured.