Why is my preemie sleeping on their tummy in the NICU?

April 18, 2021

I'm katie, OTD, OTR/L, NTMTC, CNT & founder of blooming littles

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Do you have a premature baby? Cared for one?
If so, you may be used to seeing them asleep on their tummy while in their isolette or crib. You may even have said, “They love to be on their belly.”
There are some reasons babies in the NICU LOVE resting on their tummy.
And….it’s not just because it helps them sleep!

Please remember the importance of “Back to Sleep”. It is not safe or recommended for babies to sleep on their tummies in the home environment. Babies in the NICU are placed on a monitor that continually assesses their breathing and cardiorespiratory status. This monitor and the presence of medical complexities allow us to position babies in a variety of positions during the day for sleep. 

Before your baby’s days of “Back to Sleep” arrive, let’s talk about some AMAZING reasons why babies in the NICU are placed on their bellies for sleep.

1. It’s easier for babies to breathe on their belly.

That’s right, breathing is easier for your baby when they’re positioned on their belly. This is important because many babies in the NICU need support for breathing and may need different types of medical devices to help. When babies are placed on their belly, gravity helps them expand their rib cage and lungs, so their muscles don’t have to work so hard. 

If a baby in the NICU is having a difficult time keeping their oxygen saturations in a good place, the nurse may place them on their belly in their incubator to support breathing. It may help their oxygen saturations improve and may also support a better breathing rate.

2. It strengthens their bones.

At birth, the bones of premature babies are weak and underdeveloped. They are soft, not hard like ours. The earlier a baby is born, the more susceptible they are to having weak bones.

When babies are born early, their skeletal system hasn’t had consistent deep pressure on their bones and joints from moving around in mom’s belly to build stronger bones. In the medical field, we call this proprioceptive input.

Tummy time is an AMAZING tool to support bone strength.


When babies are on their belly, they are bearing weight through their arms and legs. This deep pressure into their joints helps stimulate bone formation and strengthens those shoulders and hips. If your baby is in a good, tucked position, they’re receiving the benefits of weight bearing and building stronger bones.

Check out this sweet moment when a mama is giving her preemie a hand hug while she rests comfortably on her tummy. 

3. It builds strength and regulation of muscle tone.

Let’s build on the topic we just talked about and take it one step further. Not only does belly time improve the strength and integrity of your baby’s bones…it builds (and regulates!) their muscle tone. 

Muscle tone is kind of like how tight or loose a muscle feels. Premature babies have a tough time regulating their muscle tone. Their early arrival disrupted their brain’s ability to learn how to move and organize their body. 

There are two big categories (with a wide range between), hypertonia and hypotonia. 

Hypertonia is characterized by stiff and rigid muscles and a lack of flexibility.

Hypotonia is when your baby has low muscle tone. They may seem weak or have “squishy” muscles. This is VERY common and a normal phase of development for infants born prematurely. 

Proprioception: that sense that tells the body where it is in space

Belly sleeping is beneficial for babies with hypotonia, because it…

  1. provides joint compression that can strengthen muscles,
  2. builds proprioception, so your baby can learn about body awareness, and
  3. strengthens their muscles as they push through their arms and legs.

4. It improves oxygen levels.

This is probably the #1 reason why bedside nurses place preemies on their tummies while they’re growing and learning to breathe. 

The belly position can lead to higher oxygen levels. In one research study, there were significantly higher oxygen levels in babies who were placed on their tummies compared to babies placed on their back. 

After transitioning from higher-level respiratory support to a lower level (like moving from a ventilator to a high flow nasal cannula), babies placed on their belly had higher oxygen rates and better oxygenation over the next 6 hours. 

Tummy positioning is a common strategy used by NICU providers when managing the respiratory capabilities of premature babies. 

5. It provides calming input to their brain and body.

Tummy time for premature babies can tell the body to calm down. I want your baby to feel calm and develop self-regulation. A part of your baby’s nervous system called the parasympathetic nervous system (PNS) is responsible for calming the body and slowing down responses after a stressful event.

The proprioception your baby gets while resting on their tummy activates the parasympathetic nervous system.

That’s an amazing thing! The PNS sends relaxing signals to the body, helps lower the breathing rate, calms the heart rate, and improves digestion. 

Have you heard of “rest and digest?” 

That’s the PNS system. It puts the brakes on the stressful body responses that occur after a “fight or flight” reaction.

Wondering if your baby is feeling stressed and living in that “fight or flight” response?


6. It supports a good body position.

With premature babies, we have the goal of developing a body position called physiologic flexion. You can sort of think of it as that sweet little baby tuck!

Physiologic flexion means there’s flexion of the shoulders, hips, and knees. The shoulders are rounded forward, and the trunk is rounded like a rainbow. 

For babies who’ve joined the world early, time spent on their tummy helps build the physiologic flexion needed for breathing and muscle development

When your baby is on their tummy, it’s activating the muscles that flex their arms, legs, and tummy muscles. Those muscles are important for your baby, because they’re responsible for bringing their hands to their face for calming or rooting, touching their hands together, supporting breathing, and building a foundation for early motor skills (like touching their toes or rolling over!).

7. It promotes good sleep.

Positioning a preemie on their tummy increases time in sleep states and decreases crying. I hear so often, “She sleeps so good on her belly!” It’s a very popular NICU position for supporting good sleep.

At some point in your baby’s journey, they will transition to what we call a “safe sleep environment”. 

Safe sleep recommendations follow the ABCDs.

Baby must be…

A— alone

B— on their back

C— in a crib 

D— if you’re drowsy, careful not to drop!

Every NICU has guidelines for supporting your baby as they learn to sleep on their back in the NICU. 

For portions of the NICU experience, tummy positioning is incredibly beneficial, supportive, and essential for appropriate development.

As the transition to discharge comes, your baby is transitioned to sleeping on their back.

Stay tuned, because next week, Mak, from Mak to Sleep is going to dive into the safe sleep environment after discharge home from the NICU. Part 2 of this post coming soon! 


The effects of supine and prone positions on oxygenation in premature infants undergoing mechanical ventilation author:Zahra Abdeyaz.

Aucott, Donohue, Atkins, & Allen, 2002). 

Shepherd, K. L., Yiallourou, S. R., Odoi, A., Yeomans, E., Willis, S., Horne, R. S., & Wong, F. Y. (2020). When does prone sleeping improve cardiorespiratory status in preterm infants in the NICU?. Sleep, 43(4), zsz256.

Wiley, F., Raphael, R., & Ghanouni, P. (2020). NICU positioning strategies to reduce stress in preterm infants: a scoping review. Early Child Development and Care, 1-18.

Montgomery, K., Choy, N. L., Steele, M., & Hough, J. (2014). The effectiveness of quarter turn from prone in maintaining respiratory function in premature infants. Journal of paediatrics and child health, 50(12), 972-977.

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