Two kinds of safety seats are made for babies:
1. Small, lightweight “infant-only” safety seats are designed for use rear–facing only. This kind can be used only as long as the baby’s head is enclosed by the top rim of the seat. The label on the seat gives the upper weight limit (17 to 22 pounds). One seat can be converted into a car bed for babies who must lie flat.
2. Larger “convertible” seats usually fit children from birth to about 40 pounds. Some new models have weight limits as high as 30 to 32 pounds for rear-facing use. These products are especially good for babies under age one who are growing more rapidly than average. It may be turned around to face the front when the baby is about one year old and at least 20 pounds.
How to choose the best seat for your baby: The simplest and least expensive car accessories models for seats usually will work as well as one with fancy features. Choose a seat that you find easy to use and that fits in your vehicle.
• Before you buy a seat, try it in your car to make sure it fits and can be buckled in tightly. If you choose a convertible seat, try it facing both rearward and forward.
• Look for the seat you can use facing the rear as long as possible. Read the labels to check weight limits. If you buy an infant-only seat, you will need a convertible seat later. Most babies need to use rear-facing convertible seats as they get larger, because they outgrow their infant-only seats before age one. Some products are made to carry a baby over 20 pounds facing the rear. Look for a seat with a higher weight limit when you shop.
Practice buckling the seat into your car before your baby’s first ride.
• You’ll save a little money for your car accessories if you buy one convertible seat to do the job from birth to 40 pounds, but an infant-only seat may be easier for you to use and may fit your new-born baby better.
• An infant-only seat can be carried with you wherever you go. It can be used at home also.
• Some infant-only seats come in two parts. The base stays buckled in the vehicle, and the seat snaps in and out. You may find these convenient.
• If you want to use a convertible seat for a new-born baby, choose one without a padded shield in front of the baby. Shields do not fit small new-born babies properly. The shield comes up too high and may make proper adjustment of the harness difficult.
What about seats for preemies?
• A baby born earlier than 37 weeks may need to use an expensive car accessories like a car bed if he or she has any possibility of breathing problems when sitting semi-reclined. Ask your baby’s doctor if your baby needs to be tested before discharge for breathing problems.
• Use a seat with the shortest distances from seat to harness strap slots, and from back to crotch strap. Use rolled blankets to keep the baby’s head from slumping. Never place any extra cushioning under or behind the baby.
What to do if your baby’s head flops forward? 
• It’s important for an infant to ride sitting semi-reclined (halfway back or 45 degrees from horizontal). In the car, you may find that the safety seat is too upright for a new baby who can’t hold up his or her head. You can put a tightly rolled bath towel under the front edge of the safety seat to tilt it back a little so your baby’s head lies back comfortably. Do not recline it too far.
Harness straps must fit snugly on the body.
• Use lowest harness slots for a new-born infant. Keep the straps in the slots at or below your baby’s shoulders for the rear-facing position.
• It is very important for harness straps to fit properly over the shoulders and between the legs. Dress your baby in clothes that keep legs free. If you want to cover your baby, buckle the harness around him first, and then put a blanket over him. A bulky snowsuit or bunting can make the harness too loose.
• To fill empty spaces and give support, roll up a couple of small blankets and tuck them in on each side of your baby’s shoulders and head. If he still slumps down, put a rolled diaper between his legs behind the crotch strap. Thick padding should not be put underneath or behind the baby.