Paramedic parents share the car seat mistake countless families are making.

Between them, Krystal Kleidon and her husband have over two decades worth of experience as paramedics, and just over four years as parents to their little boy.

In their time on the job, they’ve witnessed the immediate aftermath of horrific road accidents that have torn families like theirs apart.

“We’ve seen car seats ejected from vehicles, we’ve seen cars that have rolled over so many times you can barely tell which way is up, we’ve seen accidents where you would be certain there would be no survivors,” Krystal wrote on Facebook.

But in the cases where the children were unharmed, there was one common thread: the children were properly strapped in.

Krystal, founder of the Project Hot Mess blog, is now hoping to educate other parents about the importance of properly securing your child, as, “Between my husband and I, in our 20 years experience, we have NOT seen a single child harmed in a car accident where the child was restrained in their seat properly. Not a single one.”

As a mother, she recognises that parents can agonise over which car seat to buy; that they mentally juggle safety features, star ratings, reviews and price tags.

But ultimately that expensive, state-of-the art seat can only do so much.

"Car seats have incredible safety designs now, they are designed to cocoon your child, protect them as they roll and are thrown around in an accident," she wrote. "But they can only do this if your child is restrained properly."

Among the thousands of comments on Krystals post were many illustrative stories of near misses. Including this: "I was in a major car accident. My husband was killed, I was left fighting for my life and now a paraplegic; my three kids [aged] 2, 4 and 14 survived pretty much unharmed," the woman wrote, "Being strapped in properly saved their lives."

For more, catch the latest episode of Mamamia's parenting podcast. (Post continues below.)

Parents should always closely follow manufacturer's instructions when fitting a car seat, but Krystal advises that you ask the following questions as a starting point:

"How tight are you making the straps on your child’s seat? Can they pull their own arms out of them? Can you only fit one or two fingers underneath them [as is advisable]? Do they have a big puffy jacket on that stops them from being strapped in properly?"

If you wouldn't be confident in turning your little one's chair upside down with them sitting in, she argues, then it's time to readjust.

For more information on adjusting your child's car seat, you can read the National Health and Medical Research Council's child restraint guidelines here.