Toddler sleep sack: When to use, when to stop, and what safety says

If you have ever stood in your toddler’s room at bedtime wondering whether they still need their sleep sack, you are not alone. What once felt like a newborn essential suddenly becomes a parenting gray area. Is your baby too old for a toddler sleep sack?? Is it still safe? Will they sleep without it?

As babies grow into toddlers, sleep needs evolve, mobility increases, and safety guidelines shift. What worked beautifully at six months may feel less straightforward at eighteen or twenty-four months. And when it comes to sleep products, understanding what safety experts recommend matters just as much as what helps your child rest well. 

We consulted Dr. Candice Foy, a pediatrician and medical director of the newborn nursery at Stony Brook Children’s Hospital and Kandra Becerra, founder and certified sleep consultant at Rocky Mountain Sleeping Baby to guide you through the toddler sleep sack, when to use, when to stop, and what current safety guidance says so you can make a confident, informed decision for your child.

What is a sleep sack?

A sleep sack is a sleeveless, zippered garment designed to keep babies and toddlers warm during sleep without the need for loose blankets. It is a bodysuit with a hole for your baby’s head and two holes for their arms. 

The loose fitting ‘sack’ that comes with zipper, velcro, or snaps, or some combination of the three allows your little one to freely move their arms while the legs are enclosed within a loose fabric bag.

For toddlers, sleep sacks often come in larger sizes and may include features like foot openings to allow safe mobility while still providing warmth and a familiar sleep cue.

Sleep sacks are also called sleeping bags, wearable blankets or blanket sleepers.

Is a toddler sleep sack safe?

Even if your baby rolls onto their tummy, they have their hands and arms free, which makes sleep sacks safe. Your toddler can stand comfortably in their crib in a sleep sack, however, if your toddler likes to move around in the crib or tries to climb out of the crib, then footless sleep sacks can be a fall risk.

Are weighted sleep sacks safe for toddlers?

No. Weighted sleep sacks are not safe. 

Dr. Candice Foy explains, “American Academy of Pediatrics (AAP), CDC, and NIH have all released statements urging for their removal from the market due concerns for restricting the infant’s ability to breathe, making the heart work harder to beat, which can increase the risk of sudden infant death.” 

She further adds that this applies to any weighted product that would go over the infant’s chest (weighted blankets, swaddles, sleep sacks, etc.)

At what age can babies transition to wearing a sleep sack?

You probably wrap your newborn in a swaddle. You were told it is the best option that provides gentle comfort to your newborn struggling to sleep.

But Dr. Candice Foy recommends sleep sacks (tighter ‘premade swaddles’) even at birth, as the snug wrap can help mimic the womb, calm infant, and promote sleep. They are similar to swaddles, but easier to apply.

Even if you wrap your infant in a swaddle, it is important to keep in mind that swaddles can become dangerous sooner than you think. In a few months, your baby will start rolling over swaddles giving clear indications that they are ready to be transitioned into a sleep sack. 

Furthermore, a sleep sack that compresses the arms, chest, and body should be stopped once your baby shows signs of rolling over, and could be swapped for a sleep sack that allows your baby to move freely.

Does your toddler need a sleep sack at night?

We are sure you have asked yourself this question whether your toddler needs a sleep sack. The answer is yes. A toddler sleep sack serves several purposes –

• Reduces the risk associated with loose bedding in the crib. Unlike traditional blankets, which can bunch up or cover your baby’s face thus posing a suffocation risk, a properly fitted sleep sack stays in place throughout the night keeping your baby warm.
• Functions as a wearable blanket. Even if you put a blanket on your toddler in their crib or bed, they often kick it off during the night. Having a sleep sack on ensures your child has that extra warm layer.
• Restricts mobility. It prevents a toddler from climbing out of the crib.
• Serves as part of your toddler’s nap and bedtime routine. Once the sleep sack goes on, they know they are getting ready to go to bed. This is a great sleep association. However, Kandace explains, “Sleep sacks can help with toddler sleep training if the toddler is still in a crib as it can prevent a toddler from climbing out of the crib.”

What are the cons of toddler sleep sacks?

While sleep sacks offer many benefits for your child’s sleep, there are some potential downsides to consider, including:

• Late night diaper changes can become challenging.
• Footless sleep sacks can be a fall risk if your toddler tries to climb out of the crib.
• Bedtime routine disruption where your child refuses to wear it initially and then request it after being tucked in.
• Overwarming (if not checked) can negatively impact sleep.
• Investing in several sizes as your baby grows.

What should your toddler wear under a sleep sack?

What you make your toddler wear under a sleep sack depends on a number of factors including TOG (Thermal Overall Grade), weather, and room temperature. 

Kandace Becerra recommends, “Cotton on cotton. Cotton sleep sack, cotton pajamas. This allows for breathability and comfort.” However, she advises to adjust (add and remove layers) according to the weather and room temperature (your toddler’s room temperature should ideally be 68-72°F). 

You can add short sleeves and footless pajamas in the warmer months (while some children are comfortable in just a diaper with a thin sack), and long sleeves with footie pajamas work well in the colder months with a sleep sack of thinner cotton or fleece. 

If you are not sure, consider adding a layer of warmth more than you are wearing, which means, if you are comfortable in a t-shirt and shorts, you can make your baby wear a t-shirt onesie under a light sleep sack, but if you are wearing sweatpants/sweatshirt, a heavier sleep sack with footie pajamas are more appropriate.

Tip: A good way to know is to check your baby. If their hands are cold, and chest is cool, add a layer. If your baby’s chest feels hot, then take a layer off.

How to choose the right sleep sack for your toddler?

With so many styles, fabrics, and price points available, choosing the right sleep sack for your toddler can feel overwhelming. The good news is that effectiveness is less about brand or cost and more about fit, safety, comfort, your child’s developmental stage and family preference. 

“Price does not determine effectiveness. A more expensive sleep sack does not equal better sleep,” reminds Kandace. 

Here’s what to consider while choosing a toddler sleep sack:

1. Mobility: If your toddler is walking, climbing, or attempting to get out of the crib, sleep sacks with foot openings are preferable, especially if they are at risk of falling.
2. Age: Sleep sack styles evolve as babies grow.

• For infants under four months, pre-made swaddle sleep sacks that gently secure the arms can help soothe the startle reflex.
• After four months, babies should transition to arms-out options that allow safe rolling.
• By six months and beyond, most babies move into a traditional “bag-style” sleep sack that allows free leg movement.
• For toddlers, the focus shifts entirely to comfort and mobility rather than reflex suppression. Hence, sacks with leg holes cuffed at ankles seem more sensible and safer. 

3. Fabric quality: As toddlers have sensitive skin, breathable, natural fabrics like organic cotton, bamboo blends, or merino wool that help regulate body temperature and reduce the risk of overheating are ideal. 
4. TOG rating: TOG (Thermal Overall Grade) refers to the warmth or thermal insulation of the sleep sack. Lighter TOG options are better for summer or warmer rooms, while heavier TOG ones are suitable for colder months.
5. Sizing and fit: A sleep sack should be snug around the neckline and arm openings to prevent slipping but roomy enough at the bottom so that your toddler can kick, stretch and change positions comfortably. Avoid sizing up excessively for longevity, as an oversized sleep sack can pose safety concerns.
6. Ease of use: Choose a design with accessible zippers that allow for quick middle-of-the-night diaper changes without fully removing the garment.

When to stop using sleep sack for toddlers?

A toddler may transition out of a sleep sack according to their mobility and need. Typically, toddlers between 1-2 years may be more mobile and try to climb out of their crib or try to run with their sleep sack on.

They might try to walk around their crib and trip due to footless sleep sack. This poses a safety hazard. When you see these signs, you can consider sleep sacks with foot holes (walker sleep sacks) or transitioning to a blanket. 

Some toddlers become more verbal and they tell their parents they do not want to be in a sleep sack any more. 

On the other hand, some toddlers find safety and security in their sleep sacks. They continue to wear a sleep sack even when they are 3 or 4 years old and transition from the crib to bed. They learn to get in and out of their sleeping bag before they get up in the morning or if they need to use the toilet. 

Hence, the need to stop using a sleep sack for your toddler is more to do with your child’s evolving developmental needs rather than a fixed timeline.

Conclusion

A toddler sleep sack is not a rule of thumb. For some families, it continues to offer warmth, predictability, and a sense of security well into the toddler years. For others, it becomes unnecessary as mobility increases and independence grows. The decision to use or stop using a sleep sack is less about age and more about safety, development, and your child’s individual needs.

When chosen thoughtfully and used correctly, a sleep sack can support a safe, cozy sleep environment for your toddler. And when the time comes to transition away, your toddler will let you know through their mobility, preferences, or growing independence.

You may also like to read:

• How much sleep does a 2 year old need?
• I need help with my toddler sleep regression. What can I do?
• Toddler sleep: What to expect & how to help