The shoulder straps on an infant car seat should be at or slightly below your baby's shoulders when rear-facing. This position is crucial for safety, as it cradles the child's body effectively during a crash, preventing them from sliding up and out of the harness. If the straps are too high, they can put pressure on the neck; if they're too low, they offer inadequate restraint.
Getting this right involves adjusting the harness height. Most infant seats have at least three sets of harness slots. You don't need to remove the straps entirely to change the slot; you can usually slide the headrest and harness assembly up or down. A simple rule: with your baby securely in the seat, the straps should come straight out of the seat shell at a point level with or no more than an inch below their shoulders.
As your baby grows, you'll need to adjust the harness. A good practice is to check the strap height every time you change their clothing or at least once a month. The goal is to keep the straps in that "at or below" position until your child reaches the seat's maximum rear-facing height or weight limit, as recommended by the American Academy of Pediatrics (AAP) and the National Highway Traffic Safety Administration (NHTSA).
The snugness of the harness is just as important as its height. You should not be able to pinch any excess webbing at the shoulder; this is known as the "pinch test." A properly tightened five-point harness distributes crash forces across the strongest parts of the body—the shoulders and hips—maximizing protection.
| Common Infant Car Seat Models | Typical Number of Harness Height Positions | Adjustment Method |
|---|
| Graco SnugRide SnugFit 35 DLX | 4 positions | Headrest lift-and-slide |
| Chicco KeyFit 35 | 3 positions | Harness re-threading |
| Britax Willow Brook | 5 positions | No-rethread harness system |
| Evenflo LiteMax 35 | 4 positions | One-hand adjustable headrest |
| UPPABaby Mesa | 3 positions | Harness re-threading |
| Safety 1st Smooth Ride | 3 positions | Harness re-threading |
| Maxi-Cosi Mico Max Plus | 4 positions | Headrest lift-and-slide |
