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The Best Sleep Sacks for Babies in 2024

Updated: Apr 25

A baby wears a sleep sack and yawns

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Sleep is a precious commodity when you’re a parent and ensuring that your little one is safe and comfortable while they slumber is a top priority. Enter the sleep sack, a safer alternative to both swaddles and loose bedding that can help you and your baby both get the sleep that you need.

But what is a sleep sack? Are sleep sacks safe? And how can you choose a great sleep sack for your baby? In this article, we'll answer these questions so that your little one (and you!) can soon be sleeping soundly.

In this article:

What is a sleep sack?

A sleep sack, also known as a wearable blanket or sleep bag, is a cozy and safe alternative to traditional baby blankets. It's designed to help infants and young children stay warm without the suffocation risk posed by loose blankets.

Types of sleep sack

Sleep sacks come in multiple types to better meet the needs of children in different stages of development. These types include the following:

1. Swaddle sleep sacks

Specially designed for newborns, swaddle sleep sacks provide a sense of security and prevent a startle reflex that might wake up the baby.

They usually feature "wings" that wrap around the baby's body to keep their arms tucked in. Some brands keep the baby's arms inside the sack and zip snugly around their entire body.

A baby wearing a grey swaddle sleep sack

Just like traditional blanket swaddling, a swaddle sleep sack is intended to mimic the feeling of being in the womb, which comforts new babies and aids in better sleep.

2. Transitional Sleep Sacks

A transitional sleep sack is designed to facilitate the process of transitioning a baby from swaddling to sleeping unswaddled. It helps babies adjust to the feeling of having their arms unrestricted during sleep.

Swaddle sleep sacks generally have wings just like swaddle sleep sacks, but the wings have the option of being fastened around the baby's torso under their arms.

This means that parents can leave one or both arms free while still fastening the wings snugly around the baby’s body to provide a secure environment for sleep.

3. Traditional sleep sacks

Traditional sleep sacks are wearable blankets designed to keep a baby warm while allowing freedom of movement for their arms and legs.

Traditional sleep sacks can have sleeves or be sleeveless. They are looser in the body to allow plenty of unrestricted movement, but should be fitted well around the neck and arms to prevent the baby's head or arms from being tangled or covered by loose cloth.

4. Weighted sleep sacks

A weighted sleep sack incorporates gentle weight distribution to provide a calming and soothing effect for infants during sleep. They are designed to apply light pressure evenly across the baby's body, aiming to create a comforting sensation similar to being held or swaddled.

However, the American Academy of Pediatrics (AAP) warns that weighted sleep sacks and swaddles are potentially dangerous for infants. The added weight from these products may restrict a baby's movement and potentially make it harder for them to reposition themselves, such as rolling back over if they roll from back to tummy. This movement restriction could increase suffocation risks.

Additionally, weighted sleep sacks can potentially impact a baby's heart rate and breathing. Studies have shown that as the weight on a baby's chest increases, their pulse rate may also increase, and the level of oxygen in their blood may decrease.

Pathfinder Health recommends against using weighted sleep sacks.

5. Toddler sleep sacks

A toddler sleep sack comes in larger sizes to accommodate a growing child. Most significantly, some brands offer toddler sleep sacks with holes for the child's feet. This allows for greater freedom of movement as the child grows, including nighttime bathroom visits for potty-trained children!

How do sleep sacks help babies sleep?

A baby sleep sack is an alternative to traditional swaddling. While swaddling involves wrapping a baby snugly in a blanket or other cloth, a sleep sack provides similar benefits without the need for wrapping.

Using a sleep sack can be more convenient for parents. It's also safer for the sleeping baby because it can't come unwrapped during the night.

Swaddling or using a sleep sack helps children sleep in several ways:

  1. Maintaining proper body temperature: A sleep sack provides warmth and comfort, which can help maintain a comfortable body temperature conducive to sleep.

  2. Reducing startle reflex: Sleep sacks can reduce a baby's startle reflex and prevent sudden wakings caused by reflexive movements.

  3. Comfort and security: Sleep sacks create a snug and secure environment that simulates the womb, which often helps newborns and infants sleep better.

  4. Safety: Unweighted sleep sacks are considered safer for babies than blankets or quilts, as they eliminate the risk of loose bedding in the crib, reducing the chance of suffocation or Sudden Infant Death Syndrome (SIDS).

  5. Cue for sleep: For many children, using a sleep sack can be a consistent cue for sleep, signaling that it's time to nap or sleep once the sack is put on. This routine association can help establish a calming bedtime ritual for the child. This is especially helpful when the child is sleeping in a different or unfamiliar environment, such as a relative's house or daycare.

How to use a sleep sack

Ages for use

When to introduce a sleep sack

Most healthy babies can sleep in a sleep sack right from birth. Many parents choose to begin with swaddling or using a swaddle sleep sack and then transition to a traditional sleep sack as soon as their baby shows signs of rolling over on their own.

A baby wearing a flowered swaddle sleep sack

Generally, babies should transition out of the swaddle or swaddle sleep sack around 2 months of age, or whenever they display signs of rolling. This is to reduce the risk of SIDS and other sleep-related hazards.

Once a baby is capable of rolling, they must have their arms free so that they can raise and turn their head or roll back over onto their back.

At this time, parents can introduce a traditional sleep sack for safe and comfortable sleep.

When to transition to a regular blanket

Although parents should wait until their child is at least a year old before placing a blanket or other loose bedding into their crib, there is no fixed age by which they should stop using a sleep sack.

This transition depends on the individual child's comfort, developmental milestones, and sleep environment. Some factors to consider include:

  1. Signs of refusal: Some children may start refusing to wear a sleep sack around 18 to 24 months because it restricts their mobility. These signs of resistance can be a cue that the child is ready to transition away from using a sleep sack.

  2. Potty training: Nighttime potty training requires a child to be able to independently get to the bathroom and undress to use the toilet. A sleep sack may make it harder for a child to do this.

  3. Transition to a toddler bed: Some children may naturally stop using a sleep sack when they transition to a toddler bed, typically around 2 to 3 years old. This transition often correlates with increased independence and the ability to use bedding more effectively.

You should consider your own child's development and comfort when deciding when to transition from a sleep sack. Many toddler sleep sacks are available in sizes up to 3T, so your child can continue sleeping in one as long as they—and you—are comfortable.

When to replace a sleep sack

It's also important to regularly check the sleep sack for signs of wear and tear, as well as making sure it fits properly as your baby grows.

As a general rule, it's recommended to switch to a larger size once your baby's feet can reach the bottom of the sleep sack or if they have outgrown their current size by weight.

You should also replace a sleep sack that has holes or a malfunctioning zipper to make sure that your baby does not become tangled and their face stays uncovered.

Safe sleep practices

A baby sleeping in an empty crib

In addition to using a sleep sack correctly, it's essential to also comply with the other safe sleep practices set out by the American Academy of Pediatrics to prevent sudden infant death syndrome (SIDS).

The AAP's safe sleep recommendations include the following:

  1. Always place your baby on their back for sleep in their own sleep space, not a parent or caregiver's bed.  

  2. For naps and nighttime sleep, use a crib, bassinet, or play yard that has a firm, flat mattress and a well-fitting sheet. Avoid having your baby sleep in a reclined position in a swing, bouncer, or car seat (except while in the car).

  3. Keep your baby's crib or bassinet free of items that could cause harm. For the first year, do not place soft objects (such as a loose blanket, pillow, bumper pads, or toys) in your baby's sleep space—these could increase the risk of entrapment, suffocation, or strangulation.

  4. Make sure your baby's head and face remain uncovered during sleep.

  5. Keep the room where your baby sleeps at a comfortable temperature to prevent overheating.

Banner for Pathfinder Health parenting tips

Choosing a sleep sack

The following considerations will help you choose the best sleep sack for your baby.

Tips on choosing a sleep sack for your baby

Consider the child's age and size

The general rule of thumb is to select sleep sacks based on your child's weight and height, rather than their age.

In general, newborns should use a smaller size that allows enough room for movement but prevents their body from sliding down inside the sleep sack, which could cause suffocation. The right sleep sack for an infant should fit snugly around the torso but leave enough space for their hips and legs to move freely.

As your child grows, you can dress them in a larger size that provides more legroom and allows them to stretch out comfortably.

Ensure proper hip and leg movement

The International Hip Dysplasia Institute has outlined specific guidelines to help parents choose a sleep sack that will support proper hip development:

  1. Ensure that the sleep sack allows for proper leg movement and an open hip position.

  2. Avoid tight or restrictive materials around the hip area.

  3. Choose a size that fits your baby properly and doesn't have excess fabric that could potentially bunch up and cause discomfort, limit movement, or restrict the baby's legs.

Choose appropriate fabric

Make sure that you choose a fabric that is appropriate for the season and temperature. Different fabric options include the following:

1. Cotton muslin sleep sacks: A breathable sleep sack made of cotton muslin provides comfort for babies in warm climates.

2. Eco-friendly materials: Some sleep sacks are made from eco-friendly materials such as bamboo rayon and organic cotton, offering a sustainable option for parents.

3. Polyester sleep sacks: Polyester sleep sacks are known for their durability and may offer additional warmth compared to other materials.

4. Merino wool sleep sacks: Merino wool sleep sacks, or similar alternatives, are popular for their natural warmth and softness, making them suitable for varying temperatures.

5. Fleece sleep sacks: A fleece sleep sack keeps a baby warm in the coldest environments.

You should also check the materials used in the sleep sack and make sure they are safe for your baby's skin. Look out for any potential allergens or irritants, and opt for organic or hypoallergenic options if your baby has sensitive skin.

Other sleep sack features

Sleeves vs. sleeveless sleep sacks

Sleep sack options exist both with and without sleeves. Which option is best for your baby depends on a number of considerations:

  1. Ambient temperature: If the room where your baby sleeps tends to be on the warmer side, a sleeveless sleep sack might be more suitable as it allows for better airflow and can prevent overheating. If the room is cooler, a sleep sack with sleeves may provide additional warmth and insulation.

  2. Baby's comfort: Some babies may prefer the feeling of having their arms free, while others might feel more secure with their arms covered. Observing your baby's comfort level and any signs of overheating or chilliness can help guide your decision.

  3. Safety guidelines: If using a sleep sack with sleeves, ensure that the sleeves fit well and do not pose any risks of covering the baby's face or impeding movement.

Inverted zipper

Many sleep sacks feature an inverted zipper (one that zips from the bottom to the top, rather than vice versa). An inverted zipper on a sleep sack offers several practical benefits:

  1. Smoother diaper changes: The inverted zipper design allows for easier access to the diaper area without the need to fully unzip or remove the sleep sack, facilitating quick and hassle-free diaper changes. This is particularly convenient during nighttime diaper changes and can minimize disruption to the baby's sleep.

  2. Reduced friction: When fully zipped, the zipper pull is located at the bottom of the sleep sack, rather than at the baby's neck. This reduces the potential for irritation or discomfort caused by direct contact with the zipper pull.

  3. Safety considerations: Having the zipper pull at the bottom of the sleep sack makes it less likely that an older baby will be able to unzip the sleep sack during the night.

Recommended sleep sack products

Based on the considerations described above, Pathfinder Health recommends the following sleep sacks for different stages and needs.

Whatever type of sleep sack that you choose, always make sure to use the correct size for your baby.

Best standard sleep sack: Burt's Bees Infant Wearable Blanket

Burt's Bees Infant wearable blanket

Best for warmer weather: Kyte Baby Rayon Sleeping Bag

Kyte Baby rayon sleeping bag

Best for cold weather: Woolino 4 Season Basic Baby Sleep Bag

Woolino 4 season basic baby sleep bag

Best for newborns: Halo SleepSack swaddle

Halo sleepsack swaddle

Best for older babies and toddlers: Halo Sleepsack Toddler Sleeping Bag

Halo sleepsack toddler sleeping bag

Frequently asked questions

1. At what age should a baby be out of a sleep sack?

The age varies greatly by child. Babies should not sleep in a swaddle sleep sack past the age of 2 months. For sleep sacks that leave the arms free, when to transition depends on a child’s size, development, comfort, and readiness for nighttime potty training and a toddler bed.  

2. Can a baby wear a sleep sack if they can roll over?

Sleep sacks that allow the arms to move freely are considered safe for babies who have the ability to roll over. This way, a baby who rolls onto their tummy can lift and turn their head to the side or roll back over. Babies should always be placed on their back for sleep. 

A baby sleeping on their back

3. How long can a baby wear a weighted sleep sack?

Specifications for weighted sleep sacks vary by manufacturer. However, the American Academy of Pediatrics (AAP) and Consumer Product Safety Commission (CPSC) both caution against their use because they can restrict movement and may affect a baby’s heart and lung function. 

4. Can a baby overheat in a sleep sack?

Yes. Check your child for signs of overheating to ensure their comfort and safety while sleeping. Overheating is a risk factor for sudden infant death syndrome (SIDS). You may need to lower your baby’s room temperature, use a dehumidifier and/or fan, and reduce the layers that they wear under the sleep sack. 

5. Can a sleep sack suffocate a baby?

Sleep sacks are generally considered safe, but it's essential to ensure they are the right size for the baby and are used correctly. There have been rare incidents where an overly large sleep sack covered a baby’s face, which could lead to suffocation. 

6. Is it OK for a baby to sleep without a sleep sack?

Yes, as long as the room is kept at a comfortable temperature and the baby is dressed appropriately for sleep. Babies under 1 year should never sleep with loose bedding, so it’s essential to control the room temperature by other means. 

7. What should a baby wear under a Halo sleep sack?

Depending on the season and temperature, babies can wear anything from just a diaper to full length fleece pajamas under the sleep sack. We recommend that you dress your baby in one more layer than you would need to feel comfortable yourself.

8. What should my baby wear under a fleece sleep sack?

It depends on the room temperature. If the room is warm, a lightweight bodysuit or a short-sleeve onesie is probably enough under a fleece sleep sack. In a chillier room, a baby might need full pajamas. Always check to make sure that your baby is not overheating.

9. Should a baby wear footie pajamas in a sleep sack?

It's generally recommended to avoid adding footed pajamas underneath—the sleep sack itself should provide ample warmth and coverage for a baby's legs. Instead, opt for light pajamas or a onesie to ensure your baby stays comfortable without getting too warm.

The Takeaway

A good night's rest for your baby is a critical component of their growth and development and a sleep sack can be a wonderful way to ensure that they get that rest. As each child and family is unique, the perfect sleep sack is one that meets your specific needs and preferences. 

Remember to prioritize safety, and don't hesitate to try different options until you find the one that works best for your little one.

Bio of Kavita Naik Cherry


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