Most cribs come with an adjustable mattress support that can be set to two or three height positions. The highest setting is designed for newborns, making it easier to lay them down and pick them up without straining your back. Raising the mattress is straightforward, but the method depends on your crib’s hardware, and there are important safety limits to know before you adjust anything.
How Crib Mattress Height Adjustment Works
Standard cribs use one of two mechanisms to change the mattress height. The first is a bolt-and-screw system, where the mattress support platform attaches to the crib’s side panels at pre-drilled holes. You’ll need to unscrew the bolts on each side, move the support to the higher set of holes, and re-tighten. This takes a few minutes and usually requires a wrench or Allen key (often included with the crib). The second type uses spring clips: spring-loaded metal clips that snap into slots on the crib frame. To move the mattress up, you compress each clip, slide the support out, reposition it at the higher slot, and let the clips lock into place. No tools needed.
Before you start, remove the mattress and any bedding. Check your crib’s manual for the exact number of height positions available. Most full-size cribs offer three settings (high, middle, low), though some have only two. Have a second person hold the support steady while you secure one side, then move to the other. Once the support is locked in at the new height, give it a firm push to make sure it doesn’t wobble or shift before placing the mattress back on top.
Why the Highest Setting Is Only for Newborns
Federal crib safety regulations require a minimum distance of 26 inches between the top of the mattress support and the top of the crib rail. With a standard 6-inch-thick mattress, that leaves a 20-inch barrier between the mattress surface and the rail’s edge. This 20-inch wall is what keeps a baby from climbing or falling out.
When the mattress is at its highest position, that barrier is at its shortest. This is safe only as long as your baby can’t sit up, pull up, or otherwise generate enough movement to get over the side. The moment your baby starts hitting mobility milestones, the mattress needs to come down, not go up.
When to Lower the Mattress Instead
Crib height adjustments follow your baby’s development, not their age. Here’s the general timeline pediatricians recommend:
- Highest setting: Newborns who cannot yet roll over or push up on their arms.
- Middle setting: Babies who can sit up on their own, army-crawl, or get onto their hands and knees. This often happens around 6 months.
- Lowest setting: Babies who can pull themselves to standing. Most reach this milestone around 9 months.
- Transition to a bed: Once a child can climb out of the crib, typically between 18 months and 3 years, the crib itself is no longer safe.
If you’re searching for how to raise the mattress because your baby has outgrown the lowest setting and bending down is difficult, raising the mattress is not the solution. The low position exists to prevent falls and climbing injuries. Skipping it puts your child at serious risk.
Do Not Raise the Mattress for Reflux
Many parents search for ways to elevate a crib mattress because their baby has reflux, hoping that an incline will ease spit-up and discomfort. This is one of the most persistent pieces of outdated advice in infant care, and both the American Academy of Pediatrics and the CDC are clear on the matter: do not incline, wedge, or elevate a crib mattress.
Placing a baby on an inclined surface does not reduce reflux. What it does is increase the risk of the baby sliding to the foot of the crib and ending up in a position that can obstruct breathing. The AAP, along with pediatric gastroenterology organizations in both North America and Europe, specifically recommend against devices designed to maintain head elevation in the crib. Babies with reflux should still sleep on their back, on a firm, flat surface with only a fitted sheet.
If your baby’s reflux is severe enough to disrupt sleep, talk to your pediatrician about management strategies that don’t involve changing the sleep surface.
What to Do if Bending Into the Crib Is Difficult
Some parents need a higher mattress not because of the baby’s comfort but because of their own. Back pain, joint conditions, wheelchair use, or other physical limitations can make reaching into a low crib genuinely difficult. Raising the mattress beyond its intended highest setting is not safe, but there are alternatives.
Accessible cribs exist specifically for this situation. The Gertie Accessible Crib, for example, has sides that fold open so you can reach your baby without bending over a tall rail. These cribs are designed for parents who use wheelchairs or who have chronic pain, weakness, or fatigue. They’re expensive (around $3,330), but they solve the access problem without compromising the barrier height that keeps the baby safe.
A less expensive option is a bedside bassinet or co-sleeper that sits at the same height as your bed, with one side that opens toward you. These are designed for newborns and smaller infants and allow you to tend to your baby from a lying or seated position. Once your baby outgrows the bassinet (usually by 4 to 6 months or when they can push up on hands and knees), you’ll need to transition to a full crib.
What You Should Never Do
Some improvised solutions circulate online that are genuinely dangerous. Placing anything under the mattress to raise it, such as towels, blankets, pillows, or boards, creates an uneven surface and can introduce suffocation hazards. Stacking a second mattress inside the crib reduces the distance to the rail and makes climbing out easier. Using a mattress thicker than 6 inches has the same effect: it eats into the 26-inch safety margin that federal standards require.
Zip-tying, bungee-cording, or otherwise rigging the mattress support at a non-standard height compromises the structural integrity of the crib. The pre-drilled holes and clip slots are engineered to bear weight at specific points. Improvised attachments can fail without warning.
If your crib’s mattress support is already at the highest factory setting and it still feels too low, the crib itself may not be the right product for your situation. A bassinet for the newborn months or an accessible crib for longer-term use are safer paths than modifying a standard crib beyond its design.