Not all infant car seats are the same, so some features may look different on your own seat. Read through the instruction manual before you use it, and familiarize yourself with the seat’s features and requirements. In a rear-facing car seat, the harness straps should be slightly between or below baby’s shoulders. To set up a car seat for a baby who hasn’t arrived yet, you can usually choose the lowest set of harness slots. Once your baby is born, you’ll need to sit the baby in the car seat and check to see which harness slot works best. Choose the slots that are closest to baby’s shoulders ​without being above the shoulders. Many car seats have multiple positions for the crotch buckle. The various buckle positions allow you to move the crotch strap in close to a tiny newborn, and then to move it out later to accommodate a larger infant. Some infant car seats also have multiple height settings for the crotch buckle, allowing it to be lowered for the smallest babies so there’s room for all the buckle hardware to fit over their tiny belly. The crotch strap should be as close as possible to the baby’s body. The farther away it is, the more the baby can slouch into the gap. Slouching is dangerous because as the baby slouches, their chin can drop to their chest, which can cause them to have difficulty breathing. Some buckle positions are changed by taking the strap out of the slot and moving it to a new one. Some have a sliding mechanism or push-button system to adjust the buckle position. Loosening straps always requires two hands (this is so kids can’t figure out how to do it by themselves!). One hand will be pushing down on a tab or lifting up on a lever, while the other hand takes the shoulder straps and pulls them away from the child’s body. The easiest way to find the loosening mechanism is:

Find the tail that hangs off the edge of the car seat (near the baby’s feet).Follow the tail to where it emerges from the car seat. There will be a tab to push or a lever to lift right where the strap emerges from the car seat.While pushing down or lifting up (as appropriate for your child’s car seat) use your other hand to pull the shoulder straps forward to loosen them.

If your car seat doesn’t have a front adjuster, you’ll need to check the instruction manual to find out where you loosen and tighten the harness. Some budget infant car seats have a rear-adjust system. Place the buckle tongues into the buckle housing until they click. Some buckle tongues must be puzzled together in a specific way before you can snap them into the bottom piece of the buckle. Your car seat instruction manual will show you exactly how to work the buckle. Start by sliding the chest clip down to the baby’s belly. Keep it near the belly while tightening the straps. It only gets moved up to armpit level after the straps are properly snug. Position your body at the head of the car seat (you will need this leverage) and pull up at the shoulder straps, while keeping the chest clip low. This gathers the slack up to the shoulders. Next, remove the slack by pulling the tail. Most car seats have a tail of webbing that comes out of the seat between baby’s feet. To get the straps snug, pull firmly on that webbing tail. This video demonstrates the whole process. If your car seat doesn’t have a front adjuster, check the instructions to see how to tighten the harness. Some car seats have buckles on the back of the car seat or knobs on the side that tighten the harness. For newborns, you may find that there’s still a little bit of space between the baby and the crotch strap. If your baby slouches into this gap, you can prevent this by placing a tightly rolled ​washcloth between the baby’s diaper and the crotch strap after the baby is buckled snug in the straps. If there’s a lot of space, double check that there isn’t a closer buckle position that you missed in a previous step. The rolled washcloth trick is widely accepted by car seat safety experts as an appropriate solution to a temporary problem. You should still read through the instructions that came with your car seat, or call the manufacturer’s customer service number, to make sure the practice is OK. You might also find that your car seat has an extra infant insert or some other way to help tiny babies fit properly. Once you have the harness straps adjusted, slide the chest clip into position at baby’s armpit level. With a newborn, it can be hard to get the chest clip into position when you don’t have much space between the buckle and shoulder pads. It’s important to make sure you get the clip up there, though, because it holds the harness straps in the right position to work best in the event of a crash.

Kids typically find them uncomfortable, as they add extra pressure into the side of the child’s neck (simply pull the child’s shirt up in between the strap and the neck to keep the strap from rubbing the child’s skin, if necessary) . Covers typically make the straps twist (and twisted straps aren’t safe) They are not a safety feature, unless the manual specifically states that they are required). They are often too long for newborns, and make it impossible to get the straps properly snug and the chest clip at armpit level.

A blanket over the top of the buckled harness, then tucked in around your baby, is usually enough warmth for most situations. You might also consider a winter car seat cover if you need to be out and about with baby in cold weather.​ Choose one that goes on top of the car seat—never the type where there is a layer of fabric under the baby’s body. Don’t add any other accessories to your baby’s car seat unless they’re approved by the manufacturer or they came with the car seat.