Why Use A Sleep Sack For Baby? A Mom’s Guide To Sleep Sacks

Why readIf you’re wondering why use a sleep sack for baby, you’ll find all the answers about sleep sacks or sleeping bags here. 

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As a first-time mom, I had no idea I needed to use a sleep sack for my baby. 

I knew all about swaddling! How it helps newborn babies sleep better by providing a tight and snuggly environment similar to the mom’s womb. 

But why use a sleep sack for baby? Why not just let your baby transition from the swaddles to free sleeping? 

That’s what I thought with my firstborn baby before I learned all about the benefits of a sleep sack. 

The main purpose of a sleep sack is to keep your baby’s crib free from any loose blankets. If you’re worried your baby will get cold the American Academy of Pediatrics (AAP) recommends using a wearable blanket such as a sleep sack or a sleeping bag to keep your baby warm. 


baby in a sleep sack

Photo credit: TwoPointsCouture

Swaddles vs sleep sacks

A sleep sack can be used from the very first day of your baby’s life and up until 36 months. Swaddling, on the contrary, is only for the newborn stage. 

So how to choose which one is right for your baby? 

After delivery nurses at the hospital will wrap your baby up in a warm and cozy receiving blanket. 

You can continue using a receiving blanket – just like the one at the hospital – or a swaddle blanket up until your baby is 2 months old or till she shows the first signs of rolling. 

In the newborn stage, which is also often referred to as the 4th trimester, swaddling helps babies transition to sleeping outside of the womb. Swaddling mimics the snuggly environment of the womb and makes the baby feel secure and comfy. 

Plus it helps with keeping your baby asleep by not letting her wiggle her arms and legs and waking herself up. Babies normally outgrow the startle reflex at around 5-7 months. 

a mom holding her swaddled baby

The main difference between swaddling and sleep sacks is that swaddles are meant to tightly wrap your baby’s arms and legs with no mobility, whereas a sleep sack has holes for your baby’s arms and your little one’s legs have room for movement. 

While swaddling is very beneficial for the first months of your baby’s life it’s important to not overdo it. As soon as your baby starts to show the first sign of rolling over, swaddling becomes unsafe and should be discontinued. Plus too tight swaddling for too long increases the risk of hip dysplasia

So make sure you do the swaddling right. Do not tightly swaddle your baby’s legs straight and together. Instead, do leave some room for free hip movement. Or you can start with a swaddle sack right from the beginning. 

Related: Baby Sleep Solutions – Book Review

Can you use a sleep sack for a newborn?


Swaddling is not easy with active babies. With my baby girl, no matter how hard I tried she would manage to get out of her swaddles. 

She would fight relentlessly and free at least one of her hands EVERY TIME. I didn’t feel comfortable with her being swaddled in a receiving blanket as she moved a lot even in her sleep. So the swaddle might have ended up covering her face. 

Soon enough I just gave up on swaddling and went the easy route. I chose this Halo sleep sack swaddle that’s made for newborns.

And I loved it!

Now I could quickly tighten my baby girl’s hands – before she even had the chance to resist- and she received some room to move her legs. Plus the inverted zipper that opens at the bottom made diaper changing so much easier than with a regular swaddle. 

To sum up, you can use a sleep sack for a newborn and even with greater success than a regular swaddle. 


Why use a sleep sack for baby?

Now coming back to the main question of why even bother putting a sleeping bag on your baby. 

Once your little one outgrows the swaddles at around 2 months or with the first signs of rolling, it’s time for transitioning to a sleep sack. Why do babies need a sleep sack? 

I’m a big fan of sleep sacks for so many reasons so let me list a few benefits of sleep sacks. 


  • A sleep sack or a sleeping bag is a wearable blanket that you put on your baby to keep your little one warm in colder months. This way you keep your baby’s crib free from traditional blankets that are a huge suffocation risk. Babies are very mobile when they sleep. They roll, they crawl, they constantly move from one side of the crib to another so you don’t want to have any loose blankets in their way. While a traditional blanket can end up covering your baby’s face, the wearable sleep sack stays on your baby no matter how much she moves. 

  • A sleep sack gives your baby a similar snuggly feeling as swaddling. Your baby will feel more secure and cozy in a sleeping bag when she wakes up and will be more likely to go back to sleep without your assistance. 

  • Putting a sleep sack on your baby can be a great sleep cue. Babies love predictability and thrive on routines. You can use the sleep sack as part of your baby’s sleep routine both for the nighttime and nap time sleep. At the final stage of the routine put on the sleep sack and it will be a prompt for your little one that it’s time to go to sleep. 

  • And this is the reason I turned to sleep sacks in the first place. At around 10 months my boy started to try to climb out of his crib. As soon as I’d put him down to sleep in his crib he’d get up and grab onto crib rails with his little feet like claws. That’s where I realized how important a sleep sack is to limit my boy’s mobility. First of all, with the sleep sack on he wasn’t able to grab onto the wooden slats of the crib with his feet. And secondly, the sleeping bag won’t let him spread his legs wide enough to place one foot on top of the crib and climb over. Of course, it’s better to start using a sleep sack early on so that your baby doesn’t think that climbing out of the crib is even a possibility. I learned this the hard way. So with my second baby, I started using a sleep sack right from the beginning. 

baby crawling out of the crib


When to start using a sleep sack for baby

As your baby tries to adjust to life outside the womb make it easier for her by mimicking the environment she is used to through swaddling and white noise.

If your baby absolutely hates being swaddled you can leave her one hand out for self-soothing. Or even both hands out if your baby is a good sleeper and startle reflex is not an issue. 

While swaddling will help your little one sleep longer and better, it’s important to transition out of the swaddle at around 3 months. Even if your baby doesn’t try to roll over just yet, as I mentioned above babies need room for their legs so keeping your little one swaddled for too long is not recommended.

Gradually start preparing your baby when she is 2 months old by leaving out one hand first. And then go ahead and introduce the sleep sack. Transitioning your baby from swaddling to a sleep sack will continue to give her the same secure snuggly feeling. 


Can you use a sleep sack when the baby rolls over?

Yes, absolutely! While it’s not safe to continue swaddling your baby when she starts to roll over, the sleep sack leaves your baby’s hands free for easy movement. And because the sleep sack stays on your baby during all the movement without any risk of covering your baby’s face, you can safely use it when the baby starts to roll. 

Of course, you need to realize that as with regular blanket swaddling, the use of wearable blankets or sleep sacks that compress the arms, chest, and body should stop once your baby shows signs of starting to roll over. Choose only sleep sacks that allow your baby to move freely. And you can continue to use those sleeping bags up until your baby is 3-years-old.


What is a TOG rating of a sleep sack?

TOG stands for “thermal overall grading” and indicates how warm the material of the clothing is. TOG rating of a sleep sack helps you understand how much heat it will retain. 

You never want your baby to be too hot. Overheating increases the risk of infant sleep death, also called SIDS. That’s why it’s important to choose a sleeping bag with the right TOG rating based on the season and the baby’s room temperature.

The higher the TOG, the warmer the sleep sack. 

Most of the sleep sacks have the following TOG rating: 

  • 0.5 TOG: This is the lightest sleep sack. It will be best used in the summer, in warm climates and hot rooms. If you sleep under a light sheet then your little one will be comfortable in a sleep sack with 0.5 TOG rating.

  • 1.0 TOG: When the weather starts to get cooler and your baby needs an extra layer, you might want to switch to a sleep sack with 1.0 TOG rating.

  • 2.5 TOG: And this is the warmest sleep bag for those cold winter sleep. Even if the temperature in your baby’s room falls to the low 60s F you can still have peace of mind that your little one is warm and cozy in his 2.5 TOG sleep sack.


Best sleep sacks for baby

There is no shortage of baby sleep sacks on the market. There are lightweight sacks and fleece ones, lots with cute pattern, 100% cotton sleeping sacks to choose from. The three most popular brands that offer the best sleep sacks are Halo, Kyte Baby, and Nested Bean

I myself prefer the Nested Bean zen sleep sacks. My baby girl isn’t an easy sleeper so I love their lightly weighted pad on the chest filled with non-toxic poly beans. It mimics the feeling of mom’s palm on the baby’s chest or back for tummy sleepers like in my baby girl’s case.  You can put it on either way with the pad being on the chest or on the back. 

I used other sleep sacks too but it seems like my girl sleeps better in the Nested Bean zen one. Or at least, that’s what I want to believe 🤷‍♀️


baby sleeping in a sleep sack in her crib


How many sleep sacks does a baby need?

Every baby is unique.  If your baby doesn’t spit up much and doesn’t have diaper blowouts that often, you can easily have just 2 sleep sacks. When 1 of the sleeping bags is in the wash, you can use the other one. 

Of course, take into account the seasons too. If it gets considerably cold in winter where you live you might want to get a sleeping bag with a higher TOG rating for colder months. We don’t have that problem in California, so I use a sleep sack of the same TOG rating all year long. 

Depending on the weather, you can always put on lighter or warmer clothes underneath your baby’s sleep sack as well. The rule of thumb is to use one layer more for your baby than what you’re wearing yourself.  


When should baby stop using a sleep sack?

I stopped using a sleep sack with my son when he was around 1.5. My boy started to walk at around 10 months. By the time he was 1.5, we removed one side rail of his crib so he was free to climb in and out of his crib. That’s when it was safe for him to sleep without his sleep sack anymore. My son would wake up in the middle of the night and migrate to our bed which we were fine with.  

My baby girl is 9 months old now and sleeps in her Nested Bean sleep sack. We’ll see how long she’ll stay in her sleep sack before we stop using it. 

If you prefer for your child to stay in his bed, you might want to use the sleep sack way longer. Most brands carry sleeping bags in larger sizes up until 36 months. Some parents choose to keep their child in the sleep sack as long as 3 years old. Again the purpose of this is to limit your toddler’s mobility and desire to climb in and out of the bed at night. 

So it’s up to you and your child when would be the best time to stop using the sleep sack. If your baby loves it there is no need to rush him out of the sleep sack and into a toddler bed. And similarly, if your toddler is quite mobile and hates being in the sleep sack there is no need to force the sleep sack on her for too long. Just go with what is best for your little one. 

One Last Thing

There are a lot of benefits to using a sleep sack or a sleeping bag for your baby but it all comes down to safety first.

You want your baby’s crib to be free from any loose blankets, clothing, or toys. Plus by having limited mobility she will know the crib is for sleeping and not crawling or trying to get out out of the crib. 

By creating a safe and cozy sleep environment for your little one, you’ll be able to sleep calmly yourself knowing your baby is safe, warm, and comfortable in her crib. 


Your Turn

Are you using a sleep sack with your baby? Please share with us in the comments. 
Why Use A Sleep Sack For Baby? A Mom\'s Guide To Sleep Sacks

3 thoughts on “Why Use A Sleep Sack For Baby? A Mom’s Guide To Sleep Sacks”

  1. Pingback: When Can My Baby Sleep with a Pillow and Blanket?

  2. Pingback: What Is A Receiving Blanket? Everything A New Parent Needs To Know

  3. Pingback: Nested Bean Sleep Sack Review - Does It Improve Baby Sleep? | Zen Sack

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