Babies should ride in a rear-facing child restraint until they're a year old and weigh 20 pounds because they're considerably more at risk of spinal cord injuries until then. But 50 percent of U.S. babies now exceed 20 pounds by the time they turn 9 months old, according to the American Academy of Pediatrics. The discrepancy played a central role in the death of Timothy Patrick McCormick of Centreville, Va., earlier this year. The boy received fatal head injuries, while his mother suffered minor wounds in a collision after a Valentine's Day cookie bake. Typically those seats are 20 percent to 100 percent more costly.
Some parents decide to spend the extra money to be on the safe side.
What they hadn't planned on was the three months between when he grew to 20 pounds and reached his first birthday. Their convertible car seat was only tested for 20 pounds rear-facing. James figured Spencer would be protected adequately until he turned 1 year old. Before babies reach that age, their bones haven't developed enough to handle the disproportionate weight of their heads. In a rear-facing position, crash forces are absorbed by the back of an infant seat and spread over the full length of the baby's body.