There are three types of car seats:
These are used in the semi-upright, rear-facing position only. They hold babies from birth until they they are age 2, or have reached the maximum height and weight for their seat. According to a new study, researchers suggest car seats should be used only for protection during travel, and not as replacement for cribs.
Please note that an infant must ride rear-facing until he weighs at least 20 pounds, is at least a year old, adjusted for gestational age, and has met the rear-facing weight and height limits for his convertible seat.
Convertible Car Seats
For infants, these are used in the semi-upright, rear-facing position, with the shoulder harness threaded through the slots that are at or slightly below her shoulders.
Once a baby has less than one inch from the top of her head to the top of the seat, has reached the rear-facing weight limit (generally 30 to 35 pounds) and is more than a year old, then these seats are used in the upright, forward-facing position, with the shoulder harness threaded through the upper slots as directed by the manufacturer. Most convertible seats accommodate the forward-facing child to 40 pounds; some new seats have a forward-facing weight limit of 65 pounds. A child is too tall for a forward-facing convertible seat when her shoulders are higher than the upper harness slots or the tops of her ears are above the top of the seat. If she is too tall for her convertible seat before she is too heavy for it, move her into a new seat that will use the five-point harness system and be installed in the car with the vehicle's seat belts for up to 40 to 50 pounds depending on the seat, and then can be used as a belt-positioning booster until she fits properly in the vehicle's seat belts. This forward-facing-only seat is called a high-backed or convertible booster.
A belt-positioning booster is used for children weighing 40 to 100 pounds, and shorter than 4 feet 9 inches tall (approximate ages four to ten). The booster can be either a high-back seat, which is essential if the back of the vehicle seat is not high enough to come to the top of the child's ears, or a no-back booster that works perfectly in seats with a headrest.
For more information, see our additional content on car seats:
The National Highway Traffic Safety Administration and the American Academy of Pediatrics also have information on the new tether system that makes car seats more stable.