Easy Guide for When to Lower Your Baby's Crib Mattress

Wondering when to lower your baby’s crib to keep them safe? Get guidelines for when to lower the crib to keep your baby safe at each age and stage!

In the first year of your baby’s life there is so much development and growth!

Those first 12 months are full of them meeting new milestones while you’re tweaking their baby sleep schedules to keep up with their growing development.

One thing you’ll change every so often are the straps on your baby’s car seat to ensure they fit properly, and lowering your baby’s crib mattress accordingly to optimize safe sleep for them.

But how can you be sure when to adjust the crib height?

I’m here to help you figure out when it’s time to lower your crib and adapt your baby’s sleep setup for a safe and comfortable night’s rest.

Since I’m all about sleep safety, I make it a point to follow expert recommendations.

Let’s talk about what the American Academy of Pediatrics (AAP) says about crib safety and how to determine when it’s time to lower the crib.

AAP Crib Height Recommendations

According to a retrospective analysis conducted by the AAP, an average of 7,900 children in the US went to the ER each year due to injuries involving cribs. The most common cause of these injuries were crib falls.

I don’t point out these things to scare you. I’m hoping to give you all the information you need to easily avoid preventable sleep-related injury.

So how low should the crib mattress be when your baby is a newborn?

You’re welcome to drop the crib to the lowest setting from the very beginning. It’s safe to do so even at the newborn stage.

The downside is that it can be a little awkward, especially for new parents who are learning to put a baby to sleep for the first time.

If you don’t mind making periodic adjustments to lower the crib mattress, it can be pretty handy (and more comfortable for you!) to put your baby down on a taller crib surface.

At its tallest setting, the AAP says that the crib mattress should be no less than 26 inches below the side rail.

By the time your child is taller than 35 inches, the AAP recommends that they no longer sleep in a walled crib.

That means from age newborn to between 2 and 3 years old, you’ll need to pay attention to crib mattress height and lower it as your baby grows.

A Warning About Drop-Side Cribs

In 2011, the AAP deemed drop-side cribs unsafe and halted further sale or manufacturing of them.

If you are using a “vintage” crib that was made before 2011, make sure it still meets all of the current APP crib safety guidelines. Any drop-side cribs that have been handed down to today’s moms need to be retired.

When Should I Lower My Crib?

When to lower your crib will depend largely on your baby’s growth and development. As your baby meets new physical milestones, you’ll want to lower your crib height accordingly.

Highest crib setting

The highest crib setting is perfect for newborns who are immobile. It is often the setting you’ll use when you first transition your baby to a crib. It’s definitely the easiest crib height to put a sleeping baby in! The highest crib setting is suitable for most babies under 5 months old.

Middle Setting

When to lower the crib to middle setting will again depend on your baby’s growth and development.

Your baby will learn to sit up on their own sometime between 5-8 months old and it will be time to make another crib height adjustment.

Before your baby reaches the sitting-up milestone, make sure you lower their mattress to the middle setting. If the mattress height inside the crib is too high and your baby is able to sit up on their own, they run the risk of falling out.

Lower your crib again when your baby is close to sitting up, between 5 and 8 months old.

Lowest Setting

Before your baby can pull up to stand on their own, you should lower the mattress to its lowest point. Typically, babies start pulling up to stand between 8 and 10 months old.

Another risk of falling from the crib is climbing.

If at any age your baby shows interest in climbing, it is time to take precautions to try and keep your toddler from climbing out of the crib, or move them out of a walled crib and into a toddler bed.

You may have heard that the AAP does not recommend using bumper pads in cribs due to risk of suffocation/SIDS. Another dangerous element of bumpers is that babies may be able to use them to climb up and over the crib rail.

Mattress on the Floor

As your baby’s height grows, pay attention to how far their head reaches past the top of the rail. As soon as the side of the crib is less than 3/4ths the height of your standing baby, it’s time to lower the mattress to the floor or transition to a toddler bed.

How to Lower Crib Mattress to the Floor?

It’s only safe to lower the mattress directly to the floor if your crib has been manufactured to allow it as an option. To learn how to lower your crib mattress to the floor, consult your crib’s instruction manual.

If doing a DIY solution, make sure there isn’t a gap between the mattress and the bottom of the side railing. No one wants little limbs getting stuck in the gap.

If you’ve reached the lowest setting possible on your crib and your toddler has reached a height taller than 35”, you’ll need to transition to a toddler bed for their safety.

What Age do you Transition from Crib to Toddler Bed?

As a sleep consultant, I recommend waiting until as close to age 3 to transition to a toddler bed.

Most kids under 3 years old simply don’t understand boundaries and will have difficulty with concept of staying in their bed and room.

What Should Go Inside the Crib with Baby?

The AAP recommends for at least the first 12 months of your baby’s life, there should be no blankets, pillows, or other soft items in the crib that could cover your baby’s face.

In fact, all your baby needs in their crib for the first year is a few fitted sheets (See how many crib sheets you need here), possibly a pacifier, and how they’re dressed for sleep.

Chances are pretty good that by the time you’re transitioning to a completely lowered crib, your baby is at least a year old.

Even so, the APP recommends holding off on introducing pillows, blankets, and other soft items into the crib until they are 18 months old.

How to Put Baby Into a Lowered Crib

If you’ve grown accustomed to setting your newborn down in the crib on its highest setting, the first time you set them down on a lowered mattress might throw you for a loop.

I typically recommend setting your baby down in the crib while they’re still awake, because it helps them learn to self-soothe and develop positive sleep associations.

Still, I know there will be times when you’ll need to set down a fully asleep baby—and of course your goal will be to keep them asleep in the process!

Here are some tips for setting your baby down in a lowered crib to allow for a smooth transition, whether they are awake or asleep:

Keep your baby’s arms and legs as close to their body as you can to avoid a startle response (a swaddle or a sleep sack can achieve this well).
Try to keep your baby in a mostly supine (horizontal) position.
When your waist reaches the railing, bring your arms and your baby away from your body before bending at the waist to lower them to the mattress. (Note: you can protect your back muscles from injury if you tighten your stomach before bending at the waist.)
Allow your baby’s feet to be the first part of their body to touch the mattress.
Continue lowering your baby slowly until the last part of their body to reach the mattress is their cradled head.

If you’re short like me, it can be challenging to get your baby in and out of the crib after you’ve adjusted the height. I think I even used a small stool at times to give me an extra boost!

Just remember that a short-term discomfort is well worth your baby’s safety. I hope this gave you an easy guide to follow when determining when to lower your baby’s crib!

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Amy Motroni

I'm Amy and I'm so glad you've stopped by! As a Certified Pediatric Sleep Consultant, my goal is to walk you through the process of getting your baby to sleep, so your whole family gets the rest they need!

My blog is full of things to help you celebrate motherhood including baby nursery ideas, sleep schedules and sleep tips, fun printables, baby registry must-haves, and so much more.