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Sleep sack vs. swaddle: What’s the safest option?

Babies can’t sleep safely with a loose blanket in their crib or bassinet, so what do they sleep with to keep them feeling safe and warm? The two main options are sleep sacks or swaddles. So what is a sleep sack and what is a swaddle? They’re both essentially wearable blankets that stay on a baby without going over the face like a loose blanket could. Which is safest for your baby? We’ll look at the pros and cons of sleep sack vs. swaddle so you can choose.

Swaddled sleeping baby in a bed
Shokhina/ Shutterstock


A swaddle is the very first product babies are usually wrapped in, right from their first day at the hospital. A swaddle can be a blanket wrapped tightly to form a swaddle or it can be an item specifically made as a swaddle that fastens with velcro or another adhesive.

Swaddles are used to make a newborn infant feel safe and sleep better. Because they are used to feeling pressure around their bodies inside the womb, feeling the open air with no constriction can be stressful for them. A swaddle gives them the feeling of being held. It also prevents babies from startling themselves with the Moro reflex, an involuntary response to not having support around them. This startle reflex (which can wake them from sleep if they are not swaddled) usually disappears around three to six months of age. A swaddle keeps a baby’s arms and legs secure to prevent them from flailing.

Swaddles are safe for use in infants until they can roll over. Once they gain this skill, even doing it just once, there is a risk of them rolling over in the swaddle to be face-down. With their arms restricted, they wouldn’t be able to move out of that position and could suffocate. But as newborns that are unable to roll, swaddles are an excellent sleeping option.

Sleep sacks

A sleep sack is a wearable blanket for babies. They are a sack of fabric with three holes – one for the head and two for the arms. The body and legs of the baby stay inside a loose pouch and there is usually a zipper to get the baby in and out.

Sleep sacks are often used as the transitional product when an infant outgrows swaddles but isn’t yet ready for a blanket. Since it isn’t safe for a baby to have loose fabrics or items in the crib with them until they have greater control of their bodies to be able to move away from suffocation, a sleep sack allows a baby to feel warm and covered safely. The fabric is designed not to go over their head as long as the product is the correct size.

Sleep sacks vs. swaddles: Which is safer?

Both swaddles and sleep sacks are safe to use, but only when used properly.

A swaddle is only appropriate in the first few months after birth until a baby can roll over, a skill often gained around 4 to 6 months old. It is no longer safe to use after they can roll.

It is also important that a swaddle is put on tightly enough that it does not come loose and fall off, becoming a suffocation hazard. It is also important not to tie a swaddle too tightly to restrict airflow. Buying a swaddle with velcro or another mechanism for securing it is a good investment since both of these issues are more likely with a loose blanket being used as a swaddle.

“Swaddling is really an art form,” says neonatologist, Dr. Michael Goodstein. “And if a parent hasn’t been taught how to do it, their baby can get out of the swaddle. This leaves a loose blanket in the crib, which is a big risk factor for sleep-related deaths.” Buying a swaddle that isn’t a blanket helps this issue.

Sleep sacks are best for after a baby outgrows a swaddle. They are safe at any age (including newborn infants) as long as they are the correct size. If a sleep sack is too big, it could slip over the face. They can be used for toddlers and don’t become unsafe at any age.

For the safe sleep recommendations from the American Academy of Pediatrics, which say both swaddles and sleep sacks are safe when used correctly, visit their website.

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