You know that new babies have to go home from the hospital in a safe, properly installed car seat. If you do not have one, you can not take your baby home until you get one. Some hospitals even loan these out for those that do not yet have one. There is one other way that baby can go home, though you may never know of such a thing unless you need one. Some babies that are born early do not take to a car seat very well by the time they are ready to go home. If this is the case with your child, you may have to get or rent a baby car bed to get them safely from the hospital to your home.
Preemies often spend time in the NICU before they can go home. They often have to meet requirements that babies born at or near their due date can do when they are born. Weight is not always a requirement, but your baby must have gone a certain amount of time without a breathing/heart rate drop episode, must be able to eat from a bottle or the breast exclusively, and must be at least gaining weight at a good pace. Some babies have other requirements, depending on their condition when born. Some of these very special babies will go home in a baby car bed, so keep that possibility in mind if you give birth early.
All babies going home from the NICU will be given what is called a car seat test. If they do not pass this they will be required to go home in the baby car bed rather than a seat. The test usually lasts an hour. The requirements are typically that the baby does not have a bradycardia or apnea spell, and that their blood oxygen level stays above a certain number. Some babies have problems with the car seat and oxygen saturation for some reason and will have to ride in the car bad for a while. They will graduate to the car seat before you know it.
Don't worry if you are told that your baby will need to go home in a baby car bed rather than a car seat. The NICU where your baby stayed will know how to help you find a car bed. You are not the first parents that needed one. You will always find them online if you want to order one, though you may be in a hurry to get your baby home. If so, see about expedited shipping. You won't be able to take baby home without one. See if there are places in your community or the community near your NICU that rents them or has them for sale. Not all baby stores will have them.
Some parents choose to use the baby car bed for longer than needed because they find that the baby seems to be more comfortable in the bed than in a traditional car seat. That is fine, as long as the bed meets all safety standards just like those that a car seat must meet. Buy new if you can. If you are getting a used baby car bed, make sure it has not been in an accident. There can be internal flaws you will not see. Any seat or bed that has been in an accident should never be used again.