Choosing, installing, and using your baby’s car seat correctly can be tricky. How tricky? Believe it or not, a 2015 study in the Journal of Pediatrics found that 95 percent of car seats are installed or used wrong. Yet it’s so important to get it right. Here, we clear up the confusion and tell you what you need to know, with a handy car seat safety guide.

Buying Baby’s First Seat

Selecting the right car seat and learning how to use it properly will take longer than you think. To allow yourself enough time—and to cover the possibility of an early arrival—start shopping around your sixth month of pregnancy. For a newborn, you’re looking at two choices: an infant seat, which is always rear-facing, or a convertible seat used rear-facing. Infant seats, most often designed for babies up to 30 pounds, double as carriers. Most infant seats come with a detachable base, kept in the car, which allows you to remove the baby from the car without disturbing her. Convertible seats can be used from birth to 40-plus pounds, eliminating the need for an infant seat. If you can afford it, we recommend buying a separate infant seat because they fit small babies best. If you do choose a convertible seat, pick one with a five-point harness, which provides a more secure fit for an infant. Also, look for one that can be used rear-facing to at least 30 pounds.

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Once you decide on the type of seat you want, select a brand and model. All new car seats meet federal safety performance standards when used correctly. So the way to decide on a specific model is to figure out which one will fit your car best and will be easiest to install correctly. The key: Try before you buy. If the store allows it, try out a few floor models in the parking lot. If you can’t, make sure you can return the seat once the box is opened. When you’ve got the seat you think is right, make an appointment for an inspection with a certified child-passenger safety technician. Some vehicles are simply incompatible with some car seats. Everyone can benefit from expert guidance, but you’ll especially need it if you’ve got bucket seats, a fold-down armrest in the back seat, or seat belts that are anchored forward of the seat back. Make your appointment sooner rather than later so you can return the seat if the technician finds that it isn’t a match for your car. DaimlerChrysler’s Fit for a Kid Program (877/FIT4AKID) provides free child safety seat inspections, as do local police departments. Car Seat Data (www.carseatdata.org) has a database that lets you search for which seats work in which vehicles.

Installing the Seat

Do this in advance. You don’t want to have to figure it out in the hospital parking lot.

According to the NHTSA, the safest position in the car is whichever rear position allows the seat to be installed as tightly as possible and at the right angle. Generally, the middle of the rear seat is considered safest, but if there is an indentation or bump in that position, or some other factor that makes it difficult to install the seat properly, then move the seat next to a window.

Your main objective is to get the seat in tightly. Push down on it with your full weight with one hand while tightening the seat belt with the other. Lock the seat belt according to the vehicle’s owner’s manual instructions. The seat shouldn’t jiggle more than an inch in any direction. If it does, check to see whether the buckle is fastened right at the place where the belt turns to go through the slot in the safety seat. In this position, the belt may be able to loosen. Unfasten the buckle, twist the shorter end of the belt once, and reattach it. This will keep it tightly locked in most vehicles.

If your seat belt has a free-sliding latchplate, one through which the belt can slide even when it’s buckled, you’ll need a locking clip. All new car seats come with one. If you lose it, you can buy a replacement from the manufacturer, or from a retailer like Amazon. Here’s the right way to use it: 1) Install the seat tightly; 2) hold the two parts of the belt together at the latchplate and unbuckle it; 3) thread the belt through the locking clip, no more than one inch from the latchplate; 4) buckle the belt again.

Harness straps on a rear-facing seat should come through the slots that are at or slightly below your baby’s shoulders.

Securing Baby in the Seat

The big moment has finally arrived. Baby is going home, and he’s ready to ride in his new seat. Points to remember:

The harness straps should be tightened so that you can’t get more than two fingers between the harness and the child’s collarbone.

The harness retainer clip should be at the level of Baby’s armpits.

The seat should be reclined at a 45 degree angle. Many infant seats come with a level indicator which shows you when the seat is reclined at the right angle. If your infant’s head is flopping forward, the seat may not be reclined enough. There are a few tricks that can help you achieve the right angle if your seat doesn’t have a level indicator. If you’re using the detachable base that comes with the seat, try installing the seat without it (check the manufacturer’s instructions). Don’t worry; the seat is just as safe used alone as it is with the base. If the seat is still too upright, wedge a tightly rolled towel under the end of the seat closest to the rear of the car.

When Baby Goes Front-Facing

Simply put, your baby should be rear-facing as long as possible. Many parents think that Baby should be turned around when he weighs 20 pounds and has celebrated his first birthday. Actually, the American Academy of Pediatrics emphasizes that the 20-pound/1-year mark is the absolute earliest point at which you can consider turning your baby’s seat forward. Baby’s spine is better protected in a head-on collision — and, some experts say, in a side-impact collision — when he’s facing the rear of the car. If your baby is in an infant seat and has outgrown it (when his weight has exceeded the seat’s limit or when the top of his head is less than two inches from the top of the seat), it is safer to buy a convertible seat that faces rear until 30 or 35 pounds than it is to buy a combination convertible/booster seat. Although the latter accommodates babies as light as 20 pounds, it can’t be used rear-facing. You’ll have to buy a booster when the convertible seat is outgrown (when your child hits 40 pounds), but the trade-off in peace of mind will be worth it.

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Since some convertible seats go up to 35 pounds in a rear-facing position, your child can ride rear-facing well past his second birthday. The time to switch your child to a forward-facing position is when he has exceeded the rear-facing weight limit for his convertible seat, or when the top of his head is less than an inch from the top of his convertible seat.

When Baby goes front-facing, the harness straps should be rerouted to come through the slots that are at or slightly above his shoulders.

Since September 1999, most forward-facing seats for children up to 40 pounds have had top tethers. Cars sold after September 2000 have been equipped with corresponding anchors. A top tether is a webbed strap on the back of the seat that hooks into a bolt anchor in a vehicle’s rear deck, floor, roof, or seat back. With most child safety seats, the top tether is attached when Baby goes front-facing. (There is one convertible seat on the market that is equipped with a rear-facing top tether.) Check your seat instructions and your vehicle’s owner’s manual for specific information.

A big reason so many seats are untethered is that so many of us drive pre-2000 cars and assume we can’t use tethers. But many automakers will install the anchors for free. Contact your car manufacturer for details; you’ll find a list of the major car manufacturers’ customer service numbers at www.nhtsa.dot.gov.

You may have heard of LATCH, which stands for Lower Anchors and Tethers for Children, a system designed to simplify correct car-seat installation by eventually eliminating the need to use seat belts. In September 2002, the second phase of LATCH begins. Cars will have two sets of lower anchors in the back seat, and all infant and convertible seats will have a set of straps that attach to those lower anchors.