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How to Choose a Convertible Car Seat

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True Fit Premier Convertible Car Seat Rear-Facing

This True Fit convertible car seat from The First Years is shown rear-facing with a newborn-size doll.

©2010, Heather Corley.
Once your baby begins to outgrow the infant-only car seat, it's time to consider buying a convertible car seat, which can be used rear-facing and forward-facing. The right convertible car seat will help you keep your baby rear-facing as long as possible, and also allow you to continue using a harnessed car seat for a few years until it's time for a booster seat. Because you may be using a convertible car seat for several years, it's a good idea to thoroughly consider all of your options before you buy one.

The "Best" Car Seat

As with any other car seat, a convertible car seat sold in the U.S. must meet federal safety standards and is crash tested to those standards, or beyond, depending on the manufacturer. While some car seats may be more convenient for you than others, they all meet the same basic safety standards. The best car seat is the one that fits your baby and your vehicle, and that you can use correctly every time.

Weight Limits

Convertible car seats have two sets of weight limits. There is a lower and upper weight limit for rear-facing, and a lower and upper weight limit for forward-facing. If you've used an infant car seat until your baby weighs 20 pounds or more, you'll probably want to look for a convertible car seat with a higher rear-facing weight limit to increase the time you can keep baby facing the rear. Most convertible car seats today can be used rear-facing to at least 30 pounds. There are also many models that can be used rear-facing to 40 pounds or more.

The forward-facing weight limit also can determine how long you might be able to use the car seat. Every convertible car seat sold in the U.S. can be used forward-facing to at least 40 pounds. Again, many models go well beyond that limit, with a few convertibles topping out at 70 or more pounds. Your child is unlikely to be ready to move to a booster right at 40 pounds, since young children tend to wiggle out of position easily, so a car seat with a higher harness weight should give you some extra harness time until your child is better prepared to sit still.

Height Limits

The height limits of your convertible car seat are just as important as the weight limits! Manufacturers will list the maximum heights for rear-facing and forward-facing, but you should also watch how your baby fits in the seat to determine when it's time to switch directions or buy a bigger seat. For rear-facing, the harness slots need to be at or below baby's shoulders, and there should be at least an inch of the car seat shell above his or her head. For forward-facing, the harness slots need to be at or above baby's shoulders, and the tops of his or her ears should be below the top of the car seat shell.

A taller car seat shell and higher harness slots will give you the longest usable time. Take a measuring tape with you as you shop, so that you can measure the differences between harness heights and shell heights on various car seats.

Convertible Car Seats for Newborns

Many parents prefer to use an infant-only car seat for their newborn. However, you can start out with a convertible car seat for a newborn as long as your baby fits the car seat properly. That means your baby must weigh enough to meet the minimum rear-facing weight, and should be tall enough so that the lowest harness slots are at or below his or her shoulders. My 8.5-pound newborn fit just fine in a convertible car seat. However, my under-6-pound newborn did not.

Some convertible car seats come with infant padding to take up some of the space in a large shell and help small babies fit the harness better. If this padding came with the car seat, it's fine to use it according to manufacturer's instructions. If your baby doesn't fit properly in the convertible seat as a newborn, don't add extra padding or accessories to the seat. Use a smaller infant-only car seat until your baby grows a bit.

Ease of Installation

Before buying a convertible car seat, try it out in your vehicle. Most reputable stores will let you try installing a car seat before purchase. Be sure to install it rear-facing and forward-facing! If you intend to install the car seat with LATCh, check out the connectors, and make sure you're able to get a good fit. Also try both belt paths with the seat belt, even if you don't think you'll install it that way often. You might need to put the car seat in someone else's car some time, or you may need to move it to a position that doesn't have LATCh. Choose a car seat that you feel comfortable installing and moving around from car to car.

Adjust Everything!

As with the installation, you should be comfortable with how all of the adjustments on the car seat work. Check to see how the harness height is changed. Do you need to re=thread the harness to do that? If so, make sure you can replace the harness correctly. Consider taking a newborn-sized doll or stuffed animal with you so that you can practice buckling the harness and pulling it tight. You'll need to adjust the harness every time you use the car seat, so it's crucial that you're able to do this easily.

Overall Size

While a large car seat shell usually gives you the longest usable life for the seat, it can make for a tight fit if you have a small car, or if you need to fit more than one car seat in a seating row. In compact cars, you'll also need to double check that you can get the proper rear-facing angle with a convertible seat, since there's less space between the rear seat and front seat in small cars. When you need to fit car seats side-by-side, the measurements alone won't tell you what might work. It's better to try installing the car seats together so you can see which ones puzzle together nicely.

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