When you shop through links on our site, we may receive compensation. This educational content is not intended to be a substitute for professional medical advice.

Crib Height: When to Lower Crib Mattress Height

Medically Reviewed by Dr. Pierrette Mimi Poinsett, MD
Crib mattress height depends on your baby’s age, size, and abilities.

Are you wondering if it’s time to lower your baby’s crib mattress? Or maybe your baby has reflux, and you’re considering tilting their mattress to help.

Adjusting your crib mattress doesn’t have to be difficult, but there are a few things to consider before you begin.

We’ve created this guide to help you understand the ins and outs of altering your baby’s crib height. We’ll discuss baby sleep recommendations and mattress safety and help you recognize when it’s time to pull out the tools and adjust your little one’s crib.

Key Takeaways

  • Always place your baby on their back to sleep and avoid sleep positioners to reduce the risk of SIDS.
  • Raising the crib mattress can help with mobility, reflux, and congestion, but make sure to do it safely.
  • Lower the crib mattress when your baby can sit up or pull themselves up, usually between 5 and 8 months of age.
  • To safely incline the crib mattress, place items under the mattress, not on top of it, to create a 30-degree incline.

Baby Sleep Safety Guidelines

There are a few quintessential sleep safety basics for babies. Having a working knowledge of these standard practices will help protect your baby from sudden infant death syndrome — otherwise known as SIDS.

In 2016, the American Academy of Pediatrics (AAP) announced new sleep safety guidelines to protect babies from SIDS. There are a few key basics to follow (1).

1. Room-Sharing is Recommended

The AAP recommends sharing a room with your baby for the first six months to a year of life.

It’s critical to note that room-sharing is not the same as bed-sharing, which is a hazard to infants.

It’s important to place your baby in a separate sleeper — such as a crib or bassinet — in the same room as you during the night.

Some parents also use a co-sleeper, which keeps your baby within arm’s reach but safely on a separate sleep surface.

2. Enforce Back Sleeping

You should always place your baby on their back to reduce the risk of SIDS, never on their side or stomach. The only time it’s okay for a baby to sleep on their side or stomach is when they’re already able to roll over by themselves.

At that point, you should stop swaddling them. A baby who rolls over in a swaddle will not be able to return to their back, which creates another suffocation risk.

When they reach this stage, continue to place your baby on their back to sleep, but if they roll over independently, it’s less necessary to flip them right-side-up again.

3. Avoid Sleep Positioners

Sleep positioners may seem like a good idea, but according to the FDA, you should never use them (2).

These pose a danger because babies can either roll over and have their face pressed against the positioner itself or become trapped between the crib and the positioner (3). Both of these situations may lead to suffocation.

4. Avoid Crib Extras

Sleep positioners are not the only item you shouldn’t put in your baby’s crib. Parents should avoid all extras, including stuffed animals and toys, pillows, loose blankets, or crib bumpers. Excess clutter can pose a suffocation risk.

The only safe blanket in a crib is one that’s swaddling your infant. Sleep sacks are also an appropriate and safe choice.

Why Raise the Crib Mattress?

When you first put your baby’s crib together, you may not have set the height of their crib mattress with intention. After bringing your little one home, you may have realized that the height of the mattress was less-than-ideal.

There are reasons these specific alterations, such as raising the level of the mattress or altering its angle, can be helpful:

1. More Mobility

If your crib is too low when your baby is a newborn, it can be challenging to get them into it without nearly falling in yourself.

Moving the crib mattress up to a higher position makes it a safer environment for both your baby and you.

Even if you’re a mama graced with height, bending over into the crib might be painful if you’re recovering from a cesarean section. Raising the crib mattress up can make it easier for you to lay your baby down while you’re still healing.

2. Baby Has Reflux

Babies suffering from gastroesophageal reflux disease GERD can find it uncomfortable to sleep on their backs since laying down flat allows the acidic stomach fluids to move up toward their esophagus.

When the stomach acids reach the esophagus, it may cause a painful burning sensation. It may also cause your baby to vomit or spit up, leaving you both with long nights and little sleep.

In cases of infant reflux, having your baby sleep in an inclined position can help keep the stomach acid in your baby’s stomach. However, there is a safe way to execute this move — and it’s one we’ll discuss later in this article.

3. Baby is Congested

Congestion and mucus buildup caused by a cold or allergies can cause your baby to lose sleep and struggle to breathe throughout the night.

Safely inclining your baby’s crib mattress can help relieve the pressure caused by mucus buildup and allow your baby to both breathe and sleep better.

Safety for Adjusting Crib Mattresses

Now you know why you might want to raise your baby’s crib level and angle the mattress, but is it safe? The answer is yes — with some caveats.

It’s safe to incline your baby’s crib at an angle if they suffer from GERD or congestion. It’s also safe to raise the crib mattress to the highest setting if your baby is a newborn. But if you want to raise the mattress as your baby gets older, you should reconsider.

Your baby’s crib should be lowered by half a notch, or even an entire notch, once they can sit up. This usually happens between 5 and 8 months of age.

Once your baby can pull up on their own, you should adjust the mattress to its lowest setting for their safety.

Safely Inclining Crib Mattresses

If you have a little one experiencing GERD or congestion, you may want to incline their mattress. Never do this with an object placed on top of the mattress itself. Sleep positioners, blankets, and pillows all create a serious suffocation risk for your baby.

A safer option is to create an incline by placing items under your baby’s mattress. You can use specialty anglers, blankets, pillows, or even towels to create a 30-degree (about six inches) incline for your baby.

Simply place the items under the mattress until you reach the desired angle.

Why Lower the Crib Mattress Height?

As with raising your crib mattress, there will be times in your baby’s life when you need to lower it. As your baby grows, you will need to adjust their crib.

Lowering your baby’s crib mattress is usually done for safety reasons. No one wants their baby to fall out of the crib and onto the hard floor below, even a carpeted one!

Safety for Lowering Crib Mattresses

Lowering your baby’s crib mattress is perfectly safe — in fact, when the time is right, it will make their crib even safer. Every year, 10,000 children are taken to the emergency room for crib-related accidents, with many related to children falling out of their crib (4).

This means you’ll want to adjust your crib height more than once as your baby grows.

When to Lower Your Crib Mattress

You don’t have to adjust the crib height to the lowest setting right away, but you do want to lower it as soon as your baby can sit up.

As soon as a baby sits up, they’re on their way to pulling themselves to a standing position. A baby who pulls up can flip themselves over the crib rails if the mattress is set high enough. As your baby grows, you can lower the railing until it reaches its lowest setting.

Safety Note

Once your baby reaches 36 inches tall, it is recommended that you move them out of the crib and into a toddler bed.

How To Lower a Crib Mattress

Lowering your crib’s mattress is a little more complicated than raising it on an incline, but it’s still easy enough to do on your own. If you’re unsure about any steps, check the manufacturer’s instructions in your product manual or online.

All it takes is a few simple steps:

  • Choose height: Decide which height setting you want your crib to be at. It’s a lot easier to decide this before you start, so you aren’t doing it while holding screws in your hands.
  • Remove bedding: Take the crib sheets and mattress protector off the mattress to keep them from getting snagged or torn as you move down the mattress.
  • Make adjustments: Take the screws out of the foot of the bed, and lower the mattress to your desired setting.
    When you are done with the foot of the crib, do the same at the head and insert the screws again, ensuring the mattress is stable.
  • Reset: Refit your mattress protector and sheets onto the lowered mattress.


Do Crib Mattresses Make a Difference?

Yes, a firm and well-fitting mattress is so important for a baby’s safety and proper skeletal development. It also lowers the threat of SIDS (Sudden Infant Death Syndrome).

When Should I Adjust the Height of My Crib Mattress?

Adjust the mattress level as your baby grows. Start with the highest setting for newborns and lower it once they can roll over or sit to prevent them from climbing out.

How Many Inches Should a Crib Mattress Be?

The U.S. regulations specify that a full-sized crib mattress must be at least 27 1/4 inches x 51 1/4 inches and no more than six inches thick for safety.

Is It Safe to Put Two Mattresses In a Crib?

No, stacking mattresses can create a risk of suffocation or falling. Always follow the manufacturer’s guidelines for your specific crib.

Do I Need a Mattress Topper for My Crib?

Generally, no. Crib mattresses are specially designed to be firm for safety reasons. You should never add any plushy items like toppers, blankets, or pillows.

Lower or Higher?

There are many reasons to adjust your crib mattress’s height and angle. It’s safe to raise or lower the mattress height — as long as you do it correctly.

The important thing to remember is to follow the guidelines: keep your baby’s crib clear, and watch their development so you know when to lower their crib.

Feedback: Was This Article Helpful?
Thank You For Your Feedback!
Thank You For Your Feedback!
What Did You Like?
What Went Wrong?
Headshot of Dr. Pierrette Mimi Poinsett, MD

Medically Reviewed by

Dr. Pierrette Mimi Poinsett, MD

Dr. Pierrette Mimi Poinsett is a veteran licensed pediatrician with three decades of experience, including 19 years of direct patient clinical care. She currently serves as a medical consultant, where she works with multiple projects and clients in the area of pediatrics, with an emphasis on children and adolescents with special needs.