A new study reported breathing difficulties in infants who sleep in their car seats. While car seats are a required and valuable mode of transporting babies and children in automobiles, pediatric experts warn that leaving infants asleep in the seats outside of the automobile can create a situation where a baby's respiratory function is compromised because the baby does not lie flat in the seat. The problem is particularly associated with newborns and small infants, including premature babies, so parents of twins and multiples should be especially aware of the risk. Never leave a sleeping infant unattended in the car seat and try to minimize the time that your babies spend sleeping in their seats outside of the car.