How long should a child rear face?

A child should rear face until they reach the highest weight or height allowed by their car seat — not until a particular birthday. The American Academy of Pediatrics states that all infants should ride rear-facing starting with the first ride home from the hospital, and should continue rear-facing "as long as possible until they reach the highest weight or height allowed by their car safety seat manufacturer." Most convertible seats permit rear-facing use for two years or more, and some reach 40 to 50 lb.

This is a change from the guidance many parents remember. The old rule of thumb was a specific age — commonly two — and it was retired because it was being read as a deadline rather than a minimum. In practice, a child in a seat that rear-faces to 50 lb can often stay rear-facing to three or four, and the AAP's position is that this is better rather than merely acceptable.

In a frontal crash — the most common serious type — a rear-facing seat lets the shell take the force and spreads it across the child's whole back, head and neck together. A forward-facing harness restrains the torso while the head continues forward, and a young child's head is a large proportion of their body weight with a neck that has not finished developing. That is the whole of the argument, and it does not change at a birthday.

• Bent legs are not a problem. Children sit cross-legged comfortably and leg injuries in rear-facing children are not a documented pattern. Legroom is the most common reason parents turn a seat early and it is not a safety reason.
• Motion sickness is a real but separate issue. If it is genuinely severe, discuss it with your pediatrician rather than treating turning the seat as the only option.
• Rear-facing does not require a special seat. Any convertible rear-faces; the difference between models is how far.

The other half of the picture is the back seat. The AAP is explicit that the safest place to ride for all children younger than 13 is the back seat, independent of which direction the seat faces — see where to install a car seat.

Two limits, and whichever arrives first is the one that counts.

The height limit is the one most people miss. Rear-facing, the usual rule is that the child's head must sit at least 1 in below the top of the shell, and a tall child reaches that well before 50 lb. Check it every few months rather than waiting for the weight to arrive — what size car seat does my child need sets out the measuring routine.

State law and best practice are not the same thing, and the gap is wide here. Many state statutes require rear-facing only to age one or two, or set no direction requirement at all past infancy. Meeting the statute is the floor, not the goal: a law that permits turning a seat at two does not make turning it at two the right call when the seat rear-faces to 50 lb.

Our state law pages set out what each statute actually requires, section by section, so you can see your own state's floor. Where the law and the seat disagree, follow the seat.