A: Darlene, it's good that your sister-in-law and you talk about how to keep your baby as safe as possible. You're right that most babies who die of SIDS (Sudden Infant Death Syndrome) are found facedown in a crib, or on a soft bed or sofa. The recommendation to put babies to sleep on their backs on a firm crib mattress has cut the rate of children dying of SIDS in half.

However, your sister-in-law is also right. A recent study found that some babies have died of SIDS after falling asleep sitting up in a car seat. It is thought that when a baby falls asleep sitting up, his weak neck can allow his heavy head to flop forward and cut off his airway so he can't breathe.

For this reason, it's recommended that you only allow your baby to sit in the car seat when he's awake and you're supervising him. If he falls asleep in the car seat while you're driving, be sure that his head is not flopping down—reclining the car seat can help prevent this. As soon as possible, take him out of the car seat and place him to sleep in his crib on his back.