New parents often spend hours researching child safety seats online and soliciting advice from friends and family about which brands are the safest for their babies and friendliest to their budgets. Unfortunately, despite their efforts to find the perfect car seat, parents often encounter an imperfect fit when they strap it into their vehicles for the first time.

According to federal safety guidelines, babies must ride in a semi-reclined, rear-facing position in order to keep their heads upright and airways open. The problem is, if you place a child’s car seat in a vehicle, it often rests at an unacceptable angle, which forces parents to improvise. Many resort to rolled towels or pool noodles underneath the seat to help it sit at the appropriate angle. However, using aftermarket products to modify the angle of rear-facing car seats puts a lot of responsibility on a parent and, if not done properly, may compromise the safety of the child.

This is a situation that is far more common than you might think. I published a study in the Oct. 5 online edition of the journal Traffic Injury Prevention showing that the angles of vehicle seats and child safety seats don’t align properly nearly 42 percent of the time. There are often compatibility issues with forward-facing car seats, as well. The headrests built into some vehicles’ back seats often cannot be adjusted or removed and jut out at an angle that prevents the back of the car seat from sitting flush against the vehicle seat. While this interference is generally not dangerous, parents might have a difficult time achieving a tight, snug installation when the car seat has gaps behind it.

In all, my colleagues and I examined 59 car seats and 61 vehicles at the Injury Biomechanics Research Center at the Ohio State University College of Medicine. This totals nearly 3,600 combinations, if you consider each car seat being installed into each vehicle. We’ve determined that varying angles of seat pans in vehicles, which are located at the base of seats, and variations in designs of back seat headrests account for a surprising number of compatibility issues between car seats and the vehicles in which they are used.

Before you buy a car seat, I suggest examining your vehicle’s back seat. Make note of the amount of space available in each direction and the angle of the seat pan. Also, check the headrests to see if they are adjustable or removable, and see whether the vehicle owner’s manual requires them to be in a certain setting for car seat installations.

You may want to talk to the manager of the store where you are purchasing your car seat to see if he or she will let you try it out in your particular vehicle before you buy it. The car seat might have adequate safety ratings. But if it doesn’t fit in your vehicle, it may not be the best option for your child. If you’re worried about the safety of your existing car seat, another option is to get a car seat check from a certified technician in your local community who can give advice on properly installing the car seat.

It’s important to remember that all child car seats on the market are safe and must pass rigorous federal safety standards before they can be sold. As safety technology advances and designs are constantly improved, we end up with a huge amount of variety in the market. However, there are opportunities for vehicle manufacturers and car seat manufacturers to work more closely to resolve these compatibility issues, and I’m hoping our findings provide both with the data to do so. In the meantime, parents should be proactive about selecting a seat that is a good fit for their car and their child.

Julie Bing is a research engineer at the Injury Biomechanics Research Center at the Ohio State University College of Medicine .

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Many Child Car Seats Don’t Fit Properly in Vehicles originally appeared on usnews.com