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The Science of Sleep: Your Ultimate Guide to Swaddling your Infant for Sleep

Updated: Dec 26, 2022

Welcome to The Science of Sleep where I dive deep into the research, articles, and misconceptions surrounding parenting a little human and break it down for you! Being a nurse practitioner, I rely on evidence-based studies to shape my practice and my sleep recommendations. My goal is to stick to the science and help interpret it into something meaningful that will benefit you, the sleep deprived parent.

Being a nurse practitioner, I understand how confusing all the different tips and tricks can be when it comes to infant sleep. Today, I wanted to clear the confusion surrounding swaddling a newborn and discuss both the risks and benefits. There are many "expert opinions" out there and confusing studies. Let me break it down for you.


Why Should I Care About Swaddling?

Swaddling can be very beneficial in the first few months of a newborn's life. Put yourself in your newborn's shoes. For the past 9 months they grew in this cramped space called Mom's uterus. Whenever they would stretch, their arms would hit something. Those of you who have carried an infant can relate. How many times did your little one punch you in the ribs or kick you in the bladder? Now, imagine that all of the sudden you are not in the small dark space but in the hustling and bustling world where your arms and legs can stretch free without hitting anything. You do not recognize anything and you feel out of place. Now, this can be startling for your newborn! We swaddle to mimic that cozy feeling of the uterus. It allows for a more gradual transition to life outside of the belly.

What are the Benefits of Swaddling Newborns?

Improved sleep:

Swaddling can increase the length of sleep and calm a fussy baby! Since we are trying to mimic the cozy environment from the uterus, an infant is used to this, and it provides comfort. If your infant is very fussy or has colic, you can swaddle them to help calm them down. I typically recommend limiting swaddle use for sleep only, but it can be used in a pinch when you cannot seem to calm down your infant while awake.

Suppression of the Moro reflex:

Swaddling also helps to suppress the Moro reflex (aka the Startle reflex). The Moro reflex is present from birth until 5-7 months of age. This is involuntary and occurs typically when an infant is startled. The baby will extend their arms and legs and arch their back and then will curl them back in. Suppressing this bypasses a newborn accidentally waking up due to this reflex.

Decreased risk of premature rolling:

Swaddling decreases the risk of SIDS (sudden infant death syndrome) by making it harder to roll. Have you ever tried to roll without assistance from your arms or legs to swing your weight? Let me tell you it is hard! Now remember, swaddles are only recommended for sleep time. We want babies to practice the skill of rolling when awake as well as have the ability to move their arms and legs to gain strength.

How do I Keep my Newborn Safe While Swaddled?

Now that you understand why swaddling is so important, let's talk about how to keep your newborn safe while swaddled. If an infant is not swaddled correctly, it can increase the risk of Sudden Infant Death Syndrome (SIDS). So please, ensure you are doing this safely.

Position of swaddled infant.

A meta-analysis published in Pediatrics (2016), found that infants who were swaddled and placed on their stomach were at highest risk for SIDS, followed by infants placed on their side, then infants placed on their back. They also found that the risk of SIDS increased if infants were swaddled beyond 6 months of age. So, the key takeaway is that you always place an infant on their back. Discontinue swaddling by first signs of rolling over, which can occur around 2 months of age (or sooner).

Overheating of infant.

A swaddle is an additional layer on your child. If you decide to use a traditional baby blanket, when you wrap your child up there are many layers on them. You have to account for this when you dress them for sleep. If you do not, it can lead to overheating what can lead to SIDS. So make sure your infant is placed in at most 1 layer additional to what you would wear in that environment. For example, if you sleep in shorts, a t-shirt, and a sheet consider placing your infant in a onesie and the swaddle or 2 piece pajamas with the swaddle.


This sounds scary, and it can be. The American Academy of Pediatrics highlights the need to ensure the infant is swaddled tight enough so that the swaddle cannot come loose and cover the face but loose enough around the hips to reduce the risk of hip dysplasia. An infant that is fighting the swaddle and trying to break their arms free risk the swaddle coming loose and covering their face. This could, in turn, cause difficulty breathing and possible suffocation. So please make sure your child is swaddled appropriately and that the swaddle cannot come loose. There are specific swaddles that zip or Velcro to help prevent this.

Tightness of swaddle.

You want to ensure the swaddle is tight over the arms to prevent your infant from getting it loose and getting their arms out. However, you want it loose over their hips. This is incredibly important. An infant’s hips are still developing at this point. We want to avoid hip dysplasia, which occurs when the top of the thighbone does not sit completely in the hip socket. This can cause looseness in the joint and hip problems down the road. To prevent this, ensure that the hips and legs have the ability to move within the swaddle.

Should I Swaddle with My Child's Arms in or Out?

You may be asking yourself at this point, "wait, I thought swaddling was to decrease the risk the startle reflex wakes my child up, now you are telling me I may have to swaddle with arms out?" It was hypothesized that a newborn swaddled with arms in may increase the risk of SIDS. However, according to the American Academy of Pediatrics (my go to resource when it comes to keeping children safe and guiding my practice and recommendations), arms in does not increase the risk of SIDS. The main downside to swaddling with arms in is that it prevents a newborn from self soothing (sucking on their hand to soothe themselves). This is a personal decision that each family must weigh the positives and negatives. So do what you are most comfortable with. However, you must remember to move to arms out when they show any signs of rolling over and discontinue any velcroing over chest at the same time.

How do I Choose a Swaddle for My Newborn?

When choosing a swaddle, pick one that cannot come loose. While you can use the traditional baby blanket, many companies have made specific swaddles that either Velcro or zip closed. These can help to avoid the concern with a traditional blanket becoming lose and causing suffocation. Also, avoid swaddles that have any sort of chest compression or weight. These have not been studied enough to know if they are safe. Companies market weighted blankets to help with sleep, but these have not been studied enough and the AAP recommends avoiding them. As a nurse practitioner, weighted swaddles make me nervous. Even though the weight may seem insignificant to a parent, the added weight can increase the amount of effort it takes to breath. Until enough studies have been completed to prove these are safe, I urge you to avoid them.

When Should I discontinue the Swaddle?

Once your infant shows any signs of rolling, and I mean any signs of rolling, please discontinue the swaddle immediately. At this point, I typically recommend switching to a sleep sack if you believe your child needs the extra layer. Sleep sacks (aka wearable blankets) typically have holes for the arms and look like a sleeping bag over the legs. It allows for hip movement to avoid hip dysplasia and allows for free movement of arms. Make sure you avoid any sleep sack that has chest compression or any wings that go over the chest at this point. This can pose a risk and make it more difficult to roll over if an infant finds themselves on their stomach.

Another benefit to a sleep sack? As a child gets older, it helps discourage them from climbing out of the crib! They can safely roll around in them, and there is nothing cuter than a walking toddler in a sleep sack dragging behind them. These can be used until they are old enough and have the skills to use a blanket (usually once they transition out of the crib).

Points to Remember

  • Not every infant likes swaddling. So, if your child does not like to be swaddled, that is fine. Just make sure there is nothing loose in their crib with them.

  • Please remove the swaddle for feeds. The swaddle creates a cozy comforting state for an infant. If we keep them in this while eating, we risk them not taking a full feed and possibly waking up more frequently to feed. Also, for breastfeeding infants, the movement of an infant’s hands on Mom provides hormonal feedback for Mom to make more milk.

  • Discontinue the swaddle at any signs of rolling.

  • Ensure the swaddle is loose enough to allow free movement of the hips.

  • Always place a swaddled infant on their back.

Head over to my Facebook/Instagram to see my detailed posts on swaddling!

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