What to Wear Under a Swaddle (By Temperature)

Most parents worry more about the swaddle itself than the layers underneath.

But in reality, the base layer is one of the biggest drivers of comfort and sleep quality.

Babies cannot take off layers when they get warm — or add layers when they get cold.
So we have to set them up correctly from the start.

The simplest way to get temperature right is to choose layers based on the room temperature. Not season, not guesswork.

Below is the guidance most parents wish they had from day one.

Why room temperature dictates the outfit under the swaddle

Your baby’s thermoregulation is still developing.

The body regulates best when the layers match the actual sleep environment, which is the nursery, not the weather outside.

Room temp = the only consistent variable.

How to check room temperature accurately

Use:

• A room thermometer

• A wall-mounted digital reading

• A baby monitor with temperature display

Do not base it on “how the house feels.”

Bedrooms run cooler than living areas — especially at night. Be careful of placing the crib near a window, as this can lead to more wide temperature fluctuations. 

The simplest outfit logic

Warm room = lighter base layer
Cooler room = slightly more coverage

Think breathable — not heavy.

Cotton and bamboo bodysuits are ideal starting points. Avoid fleece, as this can lead to overheating. 

Footless pajamas also work well because they don’t trap heat at the feet (feet are poor temperature indicators anyway).

Signs baby needs fewer layers

Look for:

• Sweaty back of neck

• Flushed face

• Slightly damp hairline

If these appear, remove one layer next sleep period.

Signs baby needs more layers

Look for:

• Cooler chest (not hands)

• Fussy at initial sleep onset

• Mottled skin on torso

If these appear, add one light layer next sleep period.

Breathable > heavy

More layers do not equal better sleep.

Better thermoregulation equals better sleep.

This is why breathable fabric and temperature-responsive swaddle material makes such a noticeable difference — it allows heat to escape, instead of trapping it.

Why this matters in The Ollie Swaddle

The Ollie Swaddle (and The Alphie Sleep Pouch) fabric was designed to support airflow and help avoid the temperature swings that so easily interrupt newborn sleep.

Base layer + breathable swaddle = stable comfort.

Stable comfort = more consolidated rest.