Your Ultimate Guide to Baby Sleep Sacks (Tips & Advice)

Your Ultimate Guide to Baby Sleep Sacks (Tips & Advice)

From sleep sacks to swaddles to cycles to schedules, a lot goes into sleeping like a baby.

So what’s the deal with the baby sleep sack?

Does it help?

Does it hinder?

When can you start using one?

And when should you stop?

We’re going to take you through the ins and outs, the whys, and the whens.

Tune in for all things baby sleep sack advice.

In this article: 📝

  • What is a baby sleep sack?
  • What are the benefits of a sleep sack for babies?
  • Do pediatricians recommend sleep sacks?
  • Are sleep sacks safe?
  • Should a newborn sleep in a sleep sack?
  • Do babies sleep better with sleep sacks?
  • What should babies wear under a sleep sack?
  • When should babies stop wearing sleep sacks?
  • How to choose a sleep sack for your baby

What is a baby sleep sack?

A baby sleep sack is basically a mini wearable blanket ‒ or, as the name suggests, a little sack for your baby to sleep in.

It’s sort of like a sleeping bag with spaces for a tiny head and a pair of arms to fit through.

Sleep sacks fit just loosely enough so their adorable wearers can move their legs around a bit ‒ but not too much.

As for the arms?

They are free to explore (unless you choose a swaddle type ‒ more on that later).

Usually bound together by either a zipper or snaps, sleep sacks are very easy to get on and off.

(Hello, quick and easy diaper changes!)

Popular brands include:

What are the benefits of a sleep sack for babies?

The main benefit of a sleep sack is to keep your baby warm while they sleep.

But can’t you just use a blanket for this?

Well, here’s the thing.

The American Academy of Pediatrics (AAP) advises that, for the first year of their lives, babies do not share their sleep spaces with soft bedding or toys.

And that goes for both naps and nighttime sleep.

The AAP guidelines are in place to lower the risk of Sudden Infant Death Syndrome (SIDS), the sudden and unexpected death of a baby younger than one-year-old ‒ horrible to even think about, we know.

There’s no guaranteed way to prevent SIDS, but there are methods to help stave off the danger ‒ and creating a safe sleeping environment is one of the main ones.

The CDC has issued these guidelines to help keep your little one safe while they slumber.

Bedding like pillows and blankets is on the no-go list ‒ as is anything that could get loose and cover your baby’s mouth and nose.

Enter the sleep sack ‒ a creative way to safely keep your baby’s temperature regulated while they snooze.

Do pediatricians recommend sleep sacks?

The AAP recommends wearable blankets and layered clothing as an alternative to loose bedding.

But there is cause for some caution here.

Sleep aids like swaddles and sleep sacks are not federally regulated ‒ and are not all created equal.

Recent updates to infant sleep guidelines from the American Academy of Pediatrics have added some more information for us when it comes to choosing safe products.

They advise against using any type of weighted blanket, including weighted sleep sacks and weighted swaddles.

These weighted products are specially designed to be heavier than other types of sleep gear, with the aim of soothing your little one to keep them asleep for longer.

But anything heavy that could get in the way of your baby’s breathing has the potential to be dangerous.

So as tempting as these weighted products may be, it’s best to steer clear.

Here are the other ways to make your little one’s sleep environment safe:

Put them on their backs to sleep.

While research is still ongoing, we do know that back sleeping is proving to be the safer option.

This is likely because stomach sleeping could cause the baby to rebreathe their own exhaled air, potentially obstruct their breathing passages, and cause them to overheat.

Use a firm, flat sleep surface.

A crib is a great option.

We’ll take you through how to get your baby to sleep in one here.

Cover their mattress with a fitted sheet only.

Again, the job here is to avoid any loose bedding that could be a suffocation risk.

That includes cute little baby blankets.

Think Goldilocks temperature.

That’s not too hot and not too cold.

(More on this below.)

Pop them in their own bed rather than in yours.

The topic of co-sleeping ‒ basically sleeping next to or near your little one ‒ is contentious.

There are a lot of different opinions on it and various ways to do it.

The AAP recommends sleeping in the same room but not the same bed as the safest co-sleeping arrangement.

We’ll take you through the details here.

Transport them to their crib.

If your baby falls asleep somewhere else, like a car seat or feeding pillow, move them to a safe sleep space.

(We know, this is sometimes easier said than done.)

Are sleep sacks safe?

The short answer is yes ‒ provided they are well-made and used as intended.

Research has shown that sleep sacks are as safe (if not safer) than other kinds of baby bedding.

They keep your baby cozy while avoiding the risks of loose bedding.

To keep your baby extra safe:

  • If your sleep sack has a swaddle option, make sure to stop using it as a swaddle once your baby can roll over.
  • Steer clear of the sack if your baby has a fever, as this may increase the risk of overheating. You can also try a very light cotton sleep sack with only a diaper underneath it.
  • Even when your baby becomes a toddler and blankets are an option, it’s sleep sack OR blanket, not sleep sack AND blanket. Using both together could turn the heat up too high.
  • Make sure the sleep sack is the right size. (More on this below.)

And it’s still important to check on your little ones as they sleep.

When they’re really young, this isn’t too hard as they’ll need to eat often ‒ and usually let you know about it.

(If they don’t, the recommendation is to wake them every three to four hours to eat in the first couple of weeks.)

And what about getting too hot?

Is this a concern?

Overheating is definitely something to pay attention to.

But there’s good news.

There are sleep sacks available for every specific climate and room temperature.

There are also steps you can take to make sure that your baby doesn’t get too hot, like thinking about what they wear under their sack, for example.

That being said, it’s still really important to monitor your little one for signs of overheating, as this is a risk factor for SIDS.

Check the nape of their neck.

If you notice they are sweating, feel hot to the touch, or appear flushed, it may be time to adjust the temperature accordingly.

According to the Sleep Foundation, the optimal temperature for a baby’s room is between 61 and 72 degrees Fahrenheit, with about 68 degrees probably being the sweet spot.

But we know that it’s not always possible to precisely regulate your baby’s room temp, and the AAP doesn’t give specific temperature guidelines for baby rooms.

Rather, the recommendation is to regulate your baby’s temperature by dressing them according to the temperature conditions where you live.

Should a newborn sleep in a sleep sack?

There are no shoulds here ‒ but sleep sacks can be a great way to keep your baby warm and safe.

And a sleep sack with optional swaddle arms can be a much easier way to swaddle your baby than with a blanket.

Newborns sleep a lot ‒ as in somewhere between fourteen and seventeen hours a day (and initially in quite unpredictable sleep patterns).

Becoming a human is exhausting, and all that growing, adapting, and developing means the need for some serious recuperation time.

Any tools that will help make that happen are entitled to a proud spot on the must-have list.

And sleep sacks can certainly fit the bill.

Swaddling is one tool for helping babies sleep, and the traditional way to do it is with a thin blanket.

This practice has been around for centuries.

A swaddle is said to resemble the comfort of the womb and can be an effective way to soothe a tiny baby as they transition to the outside world.

Swaddling can also help them (and you) get some extra zzzs.

And the reason for this has a lot to do with something called the Moro (or startle) reflex.

This reflex causes babies to throw their heads back and extend their arms and legs out and then in again.

This experience can make them feel like they’re falling.

While that can sound quite alarming, it’s a totally natural response to stimulation, including being put down on their backs.

While this reflex is totally normal, it may wake your baby from what otherwise would have been a peaceful slumber.

Research has shown that swaddling may help reduce motor activity and startles, keeping baby asleep for longer periods.

But as much as we’d sometimes like to keep them wrapped up in a cocoon forever, swaddling has a Use By date.

Once babies start to roll over, swaddling ‒ whether with a blanket or a swaddle sleep sack ‒ is no longer safe.

That’s because if they do happen to roll over onto their bellies, they won’t have their arms free to roll themselves back over again.

So around the four-month mark, you may want to transition over to a sleep sack without the swaddle arms, or simply wrap the swaddle arms around your baby’s belly while leaving their arms free.

There are also transition sleep sacks that provide the security of a swaddle but allow your baby to move their arms.

With their arms out, babies are able to roll themselves over if they do happen to land belly down.

And just a heads up ‒ the transition away from the swaddle may very well coincide with a sleep regression, where any sort of sleeping pattern that has emerged flies right out the window.

(If you need support through this, your Peanut community’s here. Not easy.)

Experts also say not to start sleep training until your baby is four months old.

So yep, this could be another sleep-related first heading your way at this time.

We’re rooting for you. 🧡


Do babies sleep better with sleep sacks?

This is a tough one to answer.

While there’s not much research linking sleep sacks in particular to good sleep, there are certainly ways that they can contribute to creating the ideal snooze space.

The first has to do with temperature regulation.

Tiny babies are still learning how to maintain their body temperature ‒ a whole new skill they didn’t need in the womb.

Changes in temperature can cause them to wake up.

Sleep sacks appear to help out with thermal regulation, in that they’re better at keeping your little one’s temperature constant so that they don’t experience serious variations.

And if the sleep sack has swaddle arms, the swaddling can also help your newborn sleep for longer stretches.

What should babies wear under a sleep sack?

When it comes to the underlayer, there’s no one way to do this.

You might choose a cotton onesie, footie pajamas, or even just a diaper.

The biggest consideration here is temperature ‒ and, unsurprisingly, you’ll want to go for warmer layers in a cooler climate.

A rule of thumb, though?

Keep things as light as possible.

That means, in most cases, opt for more lightweight materials.

And you can usually leave off the hats and socks.

We dive into all you need to know about dressing your baby for sleep here.

Once you’ve got them as snug as a bug, check to see if there are any signs that they might be overheating.

If so, go lighter.

When should babies stop wearing sleep sacks?

All good things come to an end, including your baby’s time in their beloved sleep sack.

So when should you stop using a sleep sack?

Well, there are no hard and fast rules here, but it’s safe to say that if your little one’s legs are bursting out of the bottom, it might be time to move on.

Another clue that it’s time for an upgrade?

They’re able to pull down the zipper themselves.

(Hot tip: If you put it on inside out, that’s a whole lot harder ‒ just saying.)

You also may no longer need a sleep sack once your toddler is able to use a blanket.

So next question: when can your baby graduate to sleeping with a blanket?

We know that the AAP recommendation is that you avoid loose bedding until they’re twelve months.

But even once they’ve hit their first birthday, it’s still important to be cautious.

Stick to light blankets ‒ that risk of overheating still exists ‒ and be on the lookout for buttons and baubles and bling that could be a choking hazard.

Ribbons can also pose a risk.

As for pillows, your child may have to wait a little longer before enjoying this particular pleasure, as pillows still pose a risk of blocking your baby’s breathing passages.

You might want to wait to introduce them to pillows when they move into their big bed.

(Psst. If you need tips on how to move your child to a big bed, we’ve got you covered here.)

But even if they’re getting too big for a baby sleep sack, it doesn’t mean this journey’s reached its final chapter.

Wearable blankets for toddlers ‒ yep, they’re a thing ‒ might be a great addition to your winter warmers.

These often have space for feet to pop through so that your busy little body is still able to move at will.

So rather than sacking the sack, it might just be a case of graduating to a whole new level of wearable warmth.

How to choose a sleep sack for your baby

If you’re sold and ready to hit the sack, your next question is likely how to choose one.

We’re here to help.

Here’s what to consider before adding to cart (or to your baby registry 🤔):

Consider the TOG rating

Sorry, um, what?

TOG stands for Thermal Overall Grade ‒ a measurement that shows how good (or bad) a product is at retaining heat.

Many popular sleep sack brands include a TOG rating ‒ basically, the lower the rating, the lighter the garment.

And, of course, if you’re looking for something to keep your baby extra warm, you’ll want a higher rating.

The rating usually goes from 0.5 (likely made from cotton or cotton muslin) to 3.0 (a heavier sack made from something like micro-fleece).

Rule of thumb ‒ the higher the temperature in the room, the lower the TOG rating you need.

And to avoid overheating, go very cautiously on those top-range TOG sacks.

Synthetic materials like micro-fleece and polyester retain A LOT of heat and should be used with extreme caution.

(If you’re unsure, it’s always a good idea to check in with your doctor.)

It’s also important to balance the TOG rating of the sleep sack with what your little one wears underneath the sack ‒ find your happy medium.

Unless you live in a cabin in Alaska, you most likely do not need footed fleece pajamas under a TOG 3.0 sleep sack.

Think about sizing

Again, we’re looking for the sweet spot here.

You want to have your sack fit large enough that your baby doesn’t feel cramped in there but not too big that it’s loose enough to be dangerous.

While you may be able to size up for other items in your baby’s wardrobe, when it comes to sleep sacks, it’s best to get something that fits them pretty well right now.

Ensure it’s age appropriate

Anything that swaddles the arms can only be used until your little one can rollover.

But most sleep sacks provide more versatility and tend to grow with your little one.

Once they reach toddlerdom, those toes can pop through ‒ a great help now that they’re on the move.

Make it easy for you

OK, with all you have going on right now, this is a big one.

There’s no one way to do this, but opt for the fasteners that are easiest for you to use.




Whatever works to make those diaper changes as easy as possible.

You got this, mama!

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