Car seats should be at the top of every new parent's to-buy list. Not only will you need one to take your baby home from the hospital, but for every car ride thereafter. Every state requires that children up to 4 years old be secured in a car seat while riding, and most require booster seats for older children.
Motor vehicle crashes remain the leading cause of death for children ages 3-14 in the U.S. In 2009, of the 322 child passengers under age 4 who died in motor-vehicle crashes, 31 percent were riding unrestrained (see NHTSA crash test video of unrestrained infant).
Car seats can reduce fatalities of infants younger than one year by 71 percent and by 54 percent for children aged one to four years. (See our full coverage of all car seats.)
A rear-facing infant seat is the first stage. A built-in harness secures the infant, reclined at an angle typically between 30 and 45 degrees, to provide optimum protection in a crash without interfering with breathing. Infant seats can accommodate most children from birth up to about 22 lbs. or more. (See our infant seat Ratings.)
With its removable carrier and swing-up handle, an infant seat lets you move your baby in and out of the car without disturbing him. Though it might be a better value to jump into a convertible seat first, infant seats, by their design, tend to be more compact and secure infants better when compared to larger convertible models, which is why we recommend them as the first step.
Though convertible seats can be used for a newborn, they will likely fit better in an infant seat. Convertible seats are best for when a baby's weight reaches the infant seat's limit, which may be as early as 6 to 9 months old. Orienting the convertible seat in a rear-facing position until your baby is at least 1 year old and over 20 lbs. is a must. But research shows that babies up to age two are better protected rear-facing (see Rear-facing longer is better). Eventually, you can "convert" the seat to face forward, and use it that way until your toddler reaches the seat's forward-facing height and weight limits. Overall, height requirements or limits for the convertible seats we tested ranged from 19 inches to 53 inches, and weight limits from 5 pounds to 80 pounds, so they can be used for several years. (Learn more about convertible car seats for kids up to 100 pounds.)
The results from many of our tests reinforce the message that it's best not to re-use any car seat that has been in a crash, whether or not it shows visible cracks. After our tests, even models that are not visibly cracked can still show signs of being potentially compromised upon close inspection: Plastics are visibly stressed, internal structures and bars are bent or have changed position, and parts that help create a taut, secure fit became pinched or difficult to use.