Babies are getting to be too heavy for customary child safety seats, a recent study says, and the extra weight could make the seat malfunction or even collapse, says AAA. Most seats are designed for children under 40 lbs., but over 300,000 kids who should be riding in child safety seats are between 45 and 60 lbs. The number of obese children today is double what that number was 30 years ago, yet child safety seat standards haven't really changed. The options? Parents must buy a larger, more expensive seat or attempt to help their children maintain their optimal weight.