The only things that belong inside a bassinet with your newborn are a firm, flat mattress, a single fitted sheet, and your baby. That’s it. The U.S. Consumer Product Safety Commission sums it up simply: “Bare is best.” Everything else your baby needs for warmth and comfort goes on their body, not in the sleep space.
The Three Things That Go in the Bassinet
A safe bassinet setup has exactly three components: the mattress that came with the bassinet, a fitted sheet designed for that specific mattress, and your baby placed on their back. No blankets, no pillows, no stuffed animals, no bumpers. This might look sparse, but newborns don’t need cushioning or coziness inside their sleep space. They need a flat, clear surface.
The fitted sheet should be snug around the mattress with no bunching or slack. Loose fabric of any kind is a suffocation risk because very young babies cannot lift or turn their heads to pull away from soft material covering their face.
Why the Mattress Matters More Than You Think
Always use the mattress that came with your bassinet. After-market replacement mattresses are now held to strict federal safety standards requiring them to match or exceed the size of the original mattress and lie completely flat. The reason: even a small gap between the mattress edge and the bassinet wall can allow an infant to become wedged. At least one infant death has been linked to exactly this scenario, and another to a depression in the center of a worn mattress.
If the mattress feels too firm to you, that’s actually correct. A baby’s face can sink into a soft surface and restrict airflow. What feels uncomfortable to an adult is the safest option for a newborn.
How to Keep Your Baby Warm Without Blankets
Since loose blankets are off the table, your baby’s clothing does all the work. The standard approach is a onesie or footed pajama underneath a wearable blanket, commonly called a sleep sack. Sleep sacks are essentially sleeping bags with arm openings that stay on your baby’s body and can’t ride up over their face.
Sleep sacks are rated by TOG, a measure of thermal resistance. Choosing the right one depends on your room temperature:
- Above 71°F: A lightweight 0.2 or 0.3 TOG sack, or just a onesie
- 67 to 75°F: A 1.0 TOG sack, the most common weight for climate-controlled homes
- 59 to 69°F: A 2.5 TOG sack with a light layer underneath
- Below 65°F: A 3.5 TOG sack, the warmest option
A good test: touch the back of your baby’s neck or chest. If the skin feels hot or sweaty, remove a layer. Overheating is a risk factor for SIDS, so erring slightly cool is safer than overdressing.
Swaddles and When to Stop Using Them
Swaddle blankets are worn on your baby, not placed loose in the bassinet, so they’re considered sleepwear rather than bedding. Many newborns sleep better swaddled because it mimics the snugness of the womb and reduces the startle reflex that wakes them.
The critical rule: stop swaddling the moment your baby attempts to roll, not when they actually roll over successfully. Rolling is typically a four-to-six-month milestone, but some babies start trying as early as two months. A swaddled baby who rolls onto their stomach has no way to push up or reposition, which creates a serious suffocation risk. Sleep sacks, which leave the arms free, can be used from birth and work well as the next step after swaddling ends.
What Should Never Go in the Bassinet
The list of prohibited items is longer than most new parents expect:
- Loose blankets or quilts: Suffocation hazard, even thin muslin ones
- Pillows or head supports: No positional support of any kind
- Stuffed animals or loveys: Not until your child moves to a crib and is older
- Crib bumpers or mesh liners: Banned or warned against by every major safety organization
- Sleep positioners or wedges: These have been linked to infant deaths and are not recommended
- Weighted swaddles, sleep sacks, or blankets: The CPSC, CDC, NIH, and AAP all warn against these products, citing multiple infant deaths and evidence that the added pressure can restrict breathing and lower oxygen levels in developing babies
Weighted infant sleep products deserve special emphasis because they’re still widely sold despite safety warnings from every major federal health agency. The weight presses on a newborn’s chest, and because an infant’s rib cage isn’t rigid yet, it doesn’t take much pressure to obstruct breathing or affect heart function. There is no safe version of a weighted sleep product for infants.
Pacifiers Are the One Safe Addition
The AAP recommends offering a pacifier at sleep time. Studies consistently show pacifier use reduces SIDS risk, even in the presence of other risk factors. You don’t need to reinsert it if it falls out after your baby falls asleep, and if your baby refuses it, that’s fine too. Don’t attach the pacifier to a clip, string, or stuffed animal inside the bassinet.
If you’re breastfeeding, waiting until nursing is well established (typically a few weeks) before introducing a pacifier is a common approach, though the timing is flexible.
Choosing the Bassinet Itself
While the question is about what goes inside, the bassinet you choose affects safety too. Research on infant deaths in bassinets found cases where babies’ faces became wedged against solid, air-impermeable sides. Bassinets with vertical mesh sides allow airflow even if your baby shifts against the wall, making them preferable to those with padded or solid fabric panels.
Look for a bassinet that meets current CPSC safety standards (any new bassinet sold in the U.S. should). If you’re using a secondhand bassinet, check for recalls, make sure the mattress is firm and fits tightly, and confirm there are no tears in the mesh or fabric. Hand-me-down bassinets with soft, pillow-like padding on the sides or bottom are not safe, no matter how well-loved they are.