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This Is The Best Time To Give Up The Sleep Sack

The answer isn't as clear cut as you might imagine.

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Getting your baby to catch some solid zzz’s at night is a goal for any sleep-deprived parent. One solution to scoring some shut eye: sleep sacks. Similar to swaddles, sleep sacks can be used as a way to lull your baby towards bedtime — and hopefully allow all of you to sleep through the night. But like most baby milestones, it’s important to know when you should stop putting your baby in a sleep sack.

Unlike swaddling, which should only last about 4-5 months (or until your baby starts to roll over, whichever comes first), sleep sacks can take your little one from the newborn all the way up to the toddler stage. “Sleep sacks are a great alternative to blankets in your child's bassinet or crib,” Sierra Dante, a pediatric sleep consultant, tells Romper in an email. “Essentially a wearable blanket that comes in varying thicknesses and fabrics, sleep sacks help parents provide a safe sleep environment for their young babies and also provide parents with peace of mind about whether their child is warm enough at night.” And because your kiddo will toss, turn, and roll in their sleep, it’s comforting to know that they’ll be consistently snoozing at a safe temperature even if they’ve kicked off the blankets for the umpteenth time that night.

But how long is this a viable solution? If you’re wondering when it’s time to stop using a sleep sack, read on.

Here's Why You Should Use A Sleep Sack In The First Place

Parents use sleep sacks for a number of reasons. Babies are born with something called the Moro reflex, which causes them to startle easily, throwing their arms up in the air during sleep.

A sleep sack helps your baby from startling awake, and keeps them snoozing soundly. Plus, many parents prefer sleep sacks as a safer alternative to blankets or covers, which the American Academy of Pediatrics (AAP) advises parents to avoid for the first year of their children's lives. And sleep sacks also offer a safer way to sleep, especially as your child gets older. “While ensuring warmth through the night, sleep sacks can also prevent toddlers from swinging a leg over the top rail of the crib and learning to climb out before they're ready for the freedom and responsibility of a big kid bed,” says Dante.

Truly, when it comes to a sleep safe environment, you can’t beat a sleep sack. In the study, “Safe sleep for pediatric inpatients,” researchers found that sleep sacks help babies snooze better and for longer periods of time. And sleep sacks have also been known to help reduce the risk of Sudden Infant Death Syndrome (SIDS), Healthy Children reported. By using a sleep sack, you won’t have a need for a baby blanket, which can cause accidental suffocation, according to a Pediatrics study.

In addition to replacing blankets and adhering to the recommended sleeping environment for your baby, sleep sacks also keep your baby's legs out of the crib bars where, unfortunately, they could get stuck. Another Pediatrics study found that almost 10,000 children are taken to the emergency room each year with crib-related injuries.

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How Many Sleep Sacks You’ll Need & How To Use Them Properly

You might find that once your child adapts to a sleep sack, they want to wear one all the time. “A sleep sack, just like swaddling, provides that feeling of security, almost like when your little one was in the womb,” certified sleep science coach Allana Wass tells Romper. “It may also feel like a gentle hug, which potentially can soothe them to sleep.” Although it can make them feel safe and secure, your child really should only wear one only when it’s time for sleep. “You’ll want to make sure to take the sleep sack off during wake times, as your baby could become overheated during active playtime while wearing it,” adds Johnston. After all, you want to create a positive sleep environment, but help your child understand the difference between night and day. If your baby is wearing a sleep sack every night, you’ll want to have at least two so you can have a clean option when one is in the wash; if you have a younger baby who tends to have more diaper leaks at night, three or four sleep sacks might be more practical.

But Here’s When You Should Stop Using A Sleep Sack

Although sleep sacks can be used until your child is well into the toddler stage, there will come a point when you’ll have to sack the sleep sack. “Once your baby learns how to roll over, you need to switch to a sleep sack that allows their hands to remain free,” advises Wass. “When your baby starts rolling over on their belly, they won’t be able to push back up.” Of course, a sleeveless sleep sack can help keep your child warm and also hands-free so that they can stay safe in their crib should they roll over onto their tummy.

You can also switch from a sleep sack to a regular blanket when your kiddo is old enough. “I am an advocate for using sleep sacks until children are three or four-when they are more capable of keeping a blanket on themselves throughout the night,” adds pediatric sleep consultant Yasmin Johnston, in an email to Romper.

Here’s How To Tell If Your Baby Has Outgrown The Need For Their Sleep Sack

While your baby’s sleep sack should be snug, it shouldn’t be constricting, either. “Reference the sleep sacks sizing guide, which is typically on the tag,” says Johnston. “If your baby has reached the size limit, the sleep sack is becoming tight, or your baby is showing frustration with their limited mobility, it’s time to move up a size or discontinue use.” Sleep sacks are made in sizes that keep even toddlers comfortable and safe, but if your child's feet are starting to outgrow the ends of the biggest size, it may be time to move on (and out) of the sleep sack.

Another thing to be mindful of is the TOG (Thermal Overall Grade) rating, which can tell you the warmth that the sleep sack offers. “Make sure to choose one that is appropriate for the nursery temperature,” advises Johnston. That way, your baby will be warm, but not get too hot or sweaty, which will impede sleep.

Sleep sacks are a safe way to keep your baby snug as a bug in their crib. Not only can they create a positive sleep association, but they’ll make your child feel secure as well. Just be aware that someday the sleep sack may no longer be necessary for your child, consider the alternatives, and you’ll all have a good night’s sleep.

Studies cited:

Geyer, J., Smith, P., Kair, L. “Safe sleep for pediatric inpatients” 2016.

Lambert, A., Parks, S., Cottengim, C., Faulkner, M., Hauck, F., Shapiro-Mendoza, C. “Sleep-Related Infant Suffocation Deaths Attributable to Soft Bedding, Overlay, and Wedging” 2019.

Yeh, E., Rochette, L., McKenzie, L., Smith, G. “Injuries Associated With Cribs, Playpens, and Bassinets Among Young Children in the US, 1990-2008” 2011.


Sierra Dante, a pediatric sleep consultant

Allana Wass, a certified sleep science coach

Yasmin Johnston, a pediatric sleep consultant

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