Booster Seat Ok for 34 Lb Child?

Updated on October 22, 2008
K.D. asks from Schenectady, NY
4 answers

My daughter is about to turn 4 and we are considering letting her use a low-back booster seat for field trips with school. She is a bit taller than average at 40 inches, but she's only 34 lbs. Every instruction I see for boosters includes this "40 lb" indicator, but WHY? Is there a safety consideration for LESS then 40 lbs? We checked the fit of the low-back booster, and it looks GREAT - the seat belt is right where it should be. So is it okay to use BEFORE she reaches 40 lbs?

We currently have a Britax Marathon in my car, which we plan on using until her shoulders are too high for the straps, or until her ears go over the top. Either way, I sincerely doubt the Britax will be in use a year from now. My husband's car has a Cosco convertible/booster, which she has used since she was 1, and which we can continue to use (theoretically) until she's 80 lbs (or, more realistically, when her ears go over the top).

So, an additional question is, when we retire the Britax (probably before she turns 5, and probably before she gets to 40 lbs.), will it be okay to start using the low-back booster full time in my car? Or should we use the Cosco high-back full time, and leave the low-back in my husband's car for occasional trips?

Maybe I'm making a mountain out of a molehill, but I've checked so many online sites and can't figure this out. Any advice would be much appreciated!

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answers from New York on


Our daughter is getting to big for her car seat as well in my husbands spare car. The car seat was given to us from a good friend who is a police officer. This officer is a trained car seat insatller/inspector. My husbnad asked him just the other day about putting our daughter in a booster seat for his car only. (Our other cars have Britax Marathon seats so they are okay for now) The officer said it is 4 years of age or 40lbs before a booster seat. Well my daughter will be 4 in Feb and she is only about 32 lbs now so most likely 4 will come before the 40lbs. I am not worried about her safety if she is not 40lbs being in a booster at age 4. Officer said she would be fine as long as the seat is installed properly and it is used properly. Hope this helps!



answers from New York on

My daughter is 42 inches and 45 pounds and still fits very comfortably in the Marathon. So you may have some more years ahead of you in the Marathon.
A great website to check out for all car seat questions is:

I used them to install all of my car seats and their website gives out a lot of useful information. Here is what they say about using booster seats:

"Children under 40 pounds receive better protection from a child restraint with a 5-point-harness than a booster seat.1,2 Unfortunately, 29% of 3 year olds (who weigh less than 40 pounds) are inappropriately graduated to a booster seat."



answers from Albany on

The NYS mantra used to be "4 or 40 pounds" for booster seat safety.

Height is a considerable factor as well. The shoulder belt needs to sit in a very specific spot on the shoulder to ensure safety. That is why we have booster seats; to boost the child up in order for the belt to fit properly.




answers from New York on

I don't have a child old enough for a booster, but I have read this many times - every step up in a car seat, is a step down in safety. I have read that low back booster are ok, but definitely not the safest. After the Marathon, can you get another booster combination (with a 5-point harness)? You can keep her in the 5pt harness until she out grows it and then turn it into a booster.

I'm a bit of a car seat geek. We were in an accident when my son was 6 months and I got a little obsessed with car seat safety afterwards. Here is a great site with lots of information -

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