Snug as a bug: dressing your baby for sleep as temperatures change

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Dressing your baby for sleep seems like it should be simple, right? There are so many sleep products that are marketed as essential for quality sleep, but are they really necessary? Also, figuring out the right balance between where you set your thermostat and the number of layers you put on your baby can be tricky. Most people have some degree of climate control in their homes, but somehow it can feel daunting to figure out the best way to dress your baby as seasons change and temperatures fluctuate. This blog will help you figure out how to choose the right sleep attire to keep your baby comfy and cozy all night.

The Science

The way you dress your baby for sleep plays a key role in ensuring a safe and comfortable sleeping environment. Your baby's sleep attire should be safe, comfortable, and allow for thermoregulation (the process by which the body maintains a stable internal temperature).

Safety

The safest sleep attire is simple and boring. The American Academy of Pediatrics (AAP) recommends against using any loose bedding in a baby's sleep space due to the risk of suffocation and entanglement. Instead, the AAP recommends that parents use wearable blankets, or sleep sacks, to provide comfort and insulation. You should also ensure that your baby's attire does not have any buttons, bows, or other decorations that could come loose and become a choking hazard. If your baby is mobile and curious, then you may also want to avoid sleep sacks that have accessible zippers because there have been a few cases of babies getting a tooth caught in a sleep sack zipper (ouch!). We also recommend avoiding weighted sleep sacks.

Temperature

Core body temperature follows a circadian rhythm, dropping to its lowest point in the middle to last third of the night, while peripheral temperature (e.g., at your child's hands and feet) follows an opposite pattern. This temperature rhythm develops between one and 10 weeks after birth in full-term babies. As adults, we can control our thermal environment by grabbing a blanket if we get cold during the night or removing a blanket if we get too hot. Babies and young children cannot physically control their sleep environment, which means that if your baby gets too cold during the circadian drop in body temperature (around 3-4 am) or if s/he gets too hot as body temperature rises again, s/he could wake up and struggle to stay asleep thereafter. For some babies this will cause persistent night waking, while others might wake too early every day.

The microclimate around your baby's body is the most important factor in how warm or cold s/he will be. Understanding how much insulation your baby's sleep attire affords is important in determining how to dress your baby for sleep. A fabric's thermal insulation ability is measured in units called thermal overall grade (TOG) for blankets, duvets, and most sleep sacks. The higher the rating, the more heat retained by the fabric. In a room with an ambient temperature between 68 and 72 degrees (20-22 C), a TOG of 1-2.5 for a sleep sack is appropriate.

Importantly, babies have a limited ability to regulate their body temperature compared to adults, which makes them more vulnerable to overheating or chilling. While the way you dress your baby for sleep may seem intuitive, overbundling has been associated with an increased risk of sudden unexplained infant death syndrome (SUIDS). In addition, apneas, or brief pauses in breathing, increase with increasing temperature.

How can you tell if your baby is too hot or too cold?

It's important to know that many common indicators of being too hot or too cold do not apply to babies. The sweating response in infants is only 1/3 that of adults, so a sweaty baby is likely way too hot and working hard to reduce body heat. In addition, premature babies do not sweat due to immature development of sweat glands. Similarly, shivering doesn't occur right away when a newborn is cold. Shivering is a final step in the process of warming.

A good way to assess your baby's core temperature is to place two fingers on your baby's chest. If your baby's chest feels cold or hot to the touch, then you may need to modify your baby's insulation. Another way to tell if your child is too hot or cold is through body posture. Hot infants will spread out their bodies, while cold infants move into a ball/fetal position. Hot infants will also reduce body movement.

If your baby has cool hands and feet, it does not necessarily mean that s/he is too cold (remember, when the core is warm, hands and feet can be cold). However, very cold hands and feet can be uncomfortable and make it harder to fall asleep. If your baby's hands and feet feel very cold, consider holding your baby to warm his/her little hands and feet rather than adding extra layers to your baby's nighttime attire. If your baby's hands and feet are cold during your bedtime routine, consider giving your baby a warm bath before bed as part of your bedtime routine.

What should the temperature be in your baby's room?

The optimal range for ambient temperature in a baby's sleep room is between 68-72°F (20-22.2°C). This temperature range is safe and comfortable for most babies, and it helps to prevent overheating or chilling during sleep. Humidity will hold heat in your child's room, while a dry room may feel colder (see our blog on humidifiers here).

How should you dress your baby for sleep?

Clothing reduces heat loss, which is good if a baby is cold, but bad if a baby is hot. For colder nights, opt for sleepwear with a higher TOG rating to keep your baby snug and warm. On the other hand, during warmer nights, choose sleepwear with a lower tog rating to allow for better ventilation and to prevent overheating. Layering can also be an effective way to regulate your child's temperature. During cooler nights, you can add a heavier sleep sack over your child's pajamas to provide extra warmth. In contrast, on milder nights, you may opt for a single layer or a onesie with a lighter sleep sack. Some of our favorite options are listed in this blog. The infographic below provides a simple guide to optimizing your baby's temperature for sleep.

If your baby is in a swaddle, then you should stop using it once your baby is strong enough to roll (see our blog on swaddling here). Your swaddle blanket should be thin and breathable, because over-swaddling can prevent the natural overnight drop in core temperature, potentially leading to sleep disruption.

If you need a little help to figure this out or if you are facing other challenges, then please check out our other blogs and sleep class. We have blogs on schedules, naps, travel, toddler issues, and more! If you just need to talk to someone who can help you devise a sleep plan, then feel free to book a one-on-one consultation with us. We are always happy to help!

References:

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