Read the instruction manual for the safety seat as well as the owner's manual for your car. Some rear car seats are too deep and safety belts are too close together for a secure installation of a safety seat. New regulations for age-related safety seats exist. These seats have a 3-point harness. A strap comes down over each of the baby's shoulders and these buckle together at the crotch.
Some convertible seats fit full-term newborns well.
Infants who are premature, have low birth weight, have certain genetic disorders, or have episodes of not breathing may need a special car safety bed or infant seat. The safest place in most cars is the center of the back seat. The position must have compatible seat belts for the safety seat. Do not put safety seats in the front seat with an automatic air bag system. Air bags, when they inflate, can kill or badly injure a child who is secured in a car seat.