If your baby looks secure in their car seat simply because the shoulder straps are snug, you could be missing a critical safety check: hidden hip slack. A harness can be tight above but far too loose over those baby thighs, compromising the overall safety of the seat and causing your baby to slouch during the ride. To check for and correct this slack, follow these simple steps:
Check for hidden hip slack:
While your baby is fully buckled, pull the chest clip buckle all the way down toward the crotch buckle.
Pull the chest clip buckle forward towards you as far as possible.
If there is hidden hip slack, you will have been able to pull the harness towards you, revealing a noteworthy gap too loose to ride safely.
Pull the adjuster tail to tighten further, and readjust your chest clip back to armpit level.
Repeat this one more time for good measure.
For a visual of hidden hip slack, check out this short video by @countrykidscarseatsafety.