Not putting the car seat in the vehicle properly is a common mistake. There is plenty of online support to help parents figure out how to put their car seat in correctly. Parents also may try to keep their kid in a seat that doesn’t fit them right, and that will cause issues down the road. It’s not recommended that babies sit in car seats for long periods of time. They can develop a bruise on their lower back if they’re in there for longer than a few hours.