When to Lower the Crib Mattress (and How to Do It Safely)
Our crib had three mattress heights, and the manual never said plainly when to use which one. Here’s what I wish someone had told me on day one: you lower the mattress before your baby needs it, not after the first scare.
When to lower the crib mattress: the quick answer
Use the highest setting for a newborn (if your crib allows it). Lower the mattress before your baby can sit up, so they can’t lean or fall over the rail. Move it to the lowest setting before your baby learns to stand. That’s the American Academy of Pediatrics’ guidance. (HealthyChildren.org, AAP) Milestones, not birthdays, are what count.
| Setting | Use it for | Move down when |
|---|---|---|
| Highest | Newborns who can’t yet roll, push up or sit | Your baby starts rolling, pushing up on hands and knees, or trying to sit |
| Middle | Babies who are sitting or working on it | Your baby starts pulling up on furniture or the crib rails |
| Lowest | Babies who can pull up or stand | Stays here until they move to a bed |
Here’s how the three settings looked on our crib:
The milestones that mean it’s time
Every baby moves at their own pace, so watch your baby rather than the calendar. Lower the mattress as soon as you see:
- Rolling or pushing up on hands and knees. These come before sitting, and they’re your cue to get ready.
- Sitting up, or trying to. A sitting baby can lean over a high rail. Lower it now.
- Pulling up on the crib rails. Go straight to the lowest setting.
- Any time you think “they could almost get over that.” Trust that feeling.
Kelleigh’s Quick Tip: If your baby hits a new milestone during the day, lower the mattress that evening. Babies love to practice new skills at 2 a.m.
How to lower the crib mattress safely
- Check your manual for how your crib’s mattress support adjusts. Every model is a little different.
- Take everything out, including the fitted sheet.
- Get a second pair of hands. Lowering the support is much easier, and safer, with two people.
- Move the support to the new setting and make sure every bolt or hook is fully secure. It should sit level and not wobble.
- Check the fit. If you can fit more than two fingers between the mattress and the crib’s sides or ends, the gap is too big. (HealthyChildren.org, AAP)
- Check the hardware. The AAP suggests inspecting the crib for loose or damaged hardware before each assembly and weekly after that, using only the manufacturer’s replacement parts. (HealthyChildren.org, AAP)
- Put the fitted sheet back on, and nothing else: no pillows, bumpers, blankets or toys.
“My baby keeps bumping their head on the crib”
Once babies get mobile, they roll, scoot and sit up into the rails. Aiden bumped his head on the crib at about 15 months. Bumps like that are a normal part of learning to move, and bumpers aren’t the answer, because padded bumpers are a suffocation risk. I wrote more about this in baby hitting head in crib.
When to move from the crib to a bed
The AAP says to move your child to a bed when they’re 35 inches (89 cm) tall, or when the side rail is less than three-quarters of their height. (HealthyChildren.org, AAP) If your toddler starts climbing out, it’s time too, even if they’re shorter.
FAQs
When should I lower my baby’s crib mattress?
Lower it before your baby can sit up, and move it to the lowest setting before they learn to stand. Watch for rolling, pushing up on hands and knees, and pulling up.
What age do you lower a crib mattress?
It depends on your baby’s milestones rather than a set age. Many babies need the first change somewhere around the time they start sitting, and the lowest setting once they start pulling up.
Can a newborn use the lowest crib setting?
Yes, the lowest setting is safe at any age. The higher setting just saves your back for the newborn months. Always follow your crib’s manual.
How do I know if the mattress fits after lowering it?
If you can fit more than two fingers between the mattress and the sides or ends of the crib, the gap is too big.
When should my toddler move out of the crib?
When they’re 35 inches tall, the rail is less than three-quarters of their height, or they start climbing out.
My take
Lowering the crib mattress takes ten minutes and a second pair of hands, and it’s one of those jobs that’s easy to put off. Do it the moment your baby starts sitting or pulling up, check the fit while you’re at it, and you’ll sleep better too.
Questions about your own baby? Email me at kelleigh@imperfecthomemaking.com.
Happy parenting!
Related reading:
