SIDS risk is highest during early infancy. It peaks between 1 and 4 months of age and then gradually decreases. About 90% of SIDS deaths occur before 6 months. The risk is much lower after 6 months, but SIDS can still occur at any time before a baby’s first birthday. Safe-sleep guidance should therefore continue for the full first year.
Six months is not a point when the risk suddenly disappears. It is better to think of the risk as a curve that rises during the first few months and then steadily falls.
When Is SIDS Risk Highest?
Safe-sleep guidance applies in mini cribs too. If the crib requires that exact size, compare options in the 38 x 24 mini-crib mattress roundup.
The general age pattern looks like this:
| Baby’s age | General SIDS risk pattern |
|---|---|
| Birth to 1 month | SIDS is possible, but the peak period usually comes later |
| 1 to 4 months | Highest-risk period |
| 4 to 6 months | Risk generally begins to fall |
| 6 to 12 months | Risk is much lower, but not zero |
| After 12 months | The term SIDS no longer applies |
These age ranges describe population patterns. They cannot predict what will happen to an individual baby. The National Institutes of Health advises families to keep following infant safe-sleep recommendations until the first birthday.
Why Does the Risk Decrease as a Baby Grows?
Keep the decision within a safe crib mattress setup: firm, flat, snugly fitted, and free of added padding.
Researchers do not know the exact cause of SIDS. One theory is that it may happen when three things occur together:
- A baby has an unknown physical vulnerability.
- The baby is passing through a fast period of development.
- The baby encounters an outside stressor, such as stomach sleeping or smoke exposure.
During the first 6 months, a baby’s breathing, sleeping, heart rate, blood pressure, and waking responses change quickly. As this early developmental period passes, the age-related risk of SIDS becomes lower. However, age alone does not make an unsafe sleep environment safe.
Six Months Is Not the End of Safe Sleep
Review the crib mattress and SIDS guidance before treating any product feature as risk prevention.
Parents often feel relieved when their baby reaches 6 months. That relief is understandable. The highest-risk months have passed for most babies.
However, safe-sleep practices still matter from 6 to 12 months. They also reduce the risk of other sleep-related deaths, including accidental suffocation, entrapment, and strangulation.
Continue to:
- Put the baby down on their back for every nap and nighttime sleep.
- Use a firm, flat, level sleep surface intended for infant sleep.
- Use only a snug fitted sheet on the mattress.
- Keep pillows, blankets, bumpers, toys, positioners, and mattress toppers out of the sleep space.
- Give the baby a separate sleep space rather than sharing an adult bed.
- Follow the crib, bassinet, mini-crib, portable crib, or playard instructions.
The NIH describes the basic setup as a separate infant sleep area with a firm, flat, level surface and no toys, pillows, blankets, quilts, or other soft objects.
Keep the Mattress Firm After Six Months
The baby sleep surface guide brings firmness, flatness, fit, and approved product use into one practical check.
A baby reaching 6 months is not a reason to make the crib mattress softer.
Do not add:
- A foam topper
- A padded mattress cover
- A folded blanket beneath the sheet
- A pillow-like insert
- Extra cushioning intended to make the surface feel more comfortable
Infant mattresses are meant to feel firmer than adult mattresses. A firm surface should not form a deep indentation beneath the baby. The mattress must also fit the crib correctly, with a fitted sheet that stays smooth and secure.
For a mini crib, use a mattress that is approved for that exact mini-crib model. Do not assume that every mattress labeled “mini crib” will fit every mini crib.
For a playard or travel crib, use only the sleep surface supplied or specifically approved by the product manufacturer. An aftermarket mattress can create gaps, change the intended height, or interfere with how the product was designed.
This rule also applies at a grandparent’s house. An older crib, borrowed playard, or replacement mattress should be checked against the exact model instructions and current recall information before use.
What Changes When a Baby Starts Rolling?
Rolling does not mean safe-sleep guidance has ended.
Always place the baby on their back at the start of every sleep. When a baby can comfortably roll from back to stomach and stomach to back on their own, parents generally do not need to keep turning the baby over. The sleep space must remain clear because the baby may roll into anything left beside them.
Do not use a positioner, wedge, rolled towel, bumper, or pillow to hold the baby in one position.
Swaddling should stop when the baby begins showing signs of trying to roll. A baby who rolls while swaddled may have trouble using their arms and body to change position. Swaddling does not reduce SIDS risk, and weighted swaddles should not be used.
Should a Baby Move to Their Own Room at Six Months?
Current guidance recommends room sharing without bed sharing for at least the first 6 months. This means the baby sleeps in a separate crib, bassinet, portable crib, or playard in the caregiver’s room.
Reaching 6 months does not require an immediate room change. Families may continue room sharing if the sleep space still fits the baby, remains suitable for the baby’s development, and is being used according to its instructions.
A room change should not lead to a sleep-surface change that makes the setup softer or less controlled. Whether the crib is in the parents’ room or the nursery, the baby still needs:
- A firm and flat mattress
- A snug fit inside the crib
- A fitted sheet only
- An empty sleep area
- Back placement at the start of each sleep
Check current safe-sleep guidance and speak with the baby’s healthcare professional when individual health or developmental concerns affect the decision.
SIDS and SUID Are Not Exactly the Same
SIDS means sudden infant death syndrome. It describes the sudden death of a baby younger than 1 year that remains unexplained after a full investigation.
SUID means sudden unexpected infant death. It is a broader term that includes:
- SIDS
- Deaths with an unknown cause
- Accidental suffocation and strangulation in bed
This difference matters because an older infant may have a lower SIDS risk but can still face suffocation, entrapment, or strangulation hazards in an unsafe sleep setup.
A soft mattress does not become suitable just because a baby is stronger. Loose blankets do not become safe because a baby can roll. Adult beds, sofas, cushions, and armchairs remain unsafe places for infant sleep.
Does a Baby Monitor Reduce SIDS Risk?
Consumer breathing, heart-rate, oxygen, or movement monitors are not a replacement for safe sleep. Current guidance does not support using home cardiorespiratory monitors as a way to reduce SIDS risk.
A monitor may alert a caregiver to movement or sound, but it cannot make an unsafe mattress, inclined surface, adult bed, or cluttered crib safe.
Use any monitor according to its instructions. Keep cords, clips, sensor parts, and other equipment out of the baby’s reach. Continue following safe-sleep guidance even when a monitor is in use.
A Practical Timeline for Parents
From birth through 4 months
This is the period when consistency is especially important. Make sure every caregiver uses the same setup for naps and nighttime sleep.
A baby should be placed:
- On their back
- On a firm, flat, level infant sleep surface
- In a separate sleep space
- With no loose or soft items nearby
The same rules should apply at home, in child care, and during visits with relatives.
From 4 through 6 months
Rolling may begin during this stage. Stop swaddling when the baby starts trying to roll.
Check that:
- The fitted sheet remains tight.
- The mattress has not shifted.
- There are no gaps around the mattress.
- The crib mattress support is at the correct height under the crib instructions.
- No comfort items have been added.
From 6 through 12 months
The SIDS risk is lower, but infant safe-sleep guidance continues.
A growing baby may sit, pull up, or stand. Lower the crib mattress support when required by the crib instructions. Remove mobiles or other items when the manufacturer’s age or developmental limits are reached.
Do not add a topper or switch to a softer sleep surface simply because the baby is older.
After the first birthday
SIDS is defined as occurring before 1 year of age. However, the first birthday does not automatically mean every pillow, blanket, mattress, or toddler-bed setup is suitable.
A crib-to-toddler-bed transition is a separate decision. Follow the crib or bed manufacturer’s limits and current professional guidance. Continue checking for entrapment, strangulation, falls, loose parts, and unsuitable gaps.
When to Seek Individual Guidance
Ask the baby’s pediatrician or other qualified healthcare professional about sleep positioning or setup when a baby:
- Was born prematurely
- Had a low birth weight
- Has a breathing, airway, heart, muscle, or neurological condition
- Has received special sleep-positioning instructions during hospital care
- Is using prescribed medical equipment
- Has unusual movement, breathing, color, or waking concerns
Prematurity and low birth weight are associated with higher SIDS risk. Most babies, including babies with reflux, should still be placed flat on their backs unless their healthcare professional gives different instructions for a specific medical reason.
Frequently Asked Questions
At what age does SIDS risk start to decrease?
SIDS risk peaks between 1 and 4 months and generally begins to decrease after that period. About 90% of SIDS deaths occur before 6 months, but the risk continues until the first birthday.
Is SIDS still possible after 6 months?
Yes. SIDS is less common after 6 months, but it can occur at any time during the first year. Continue infant safe-sleep practices until the baby turns 1.
Can I use a softer crib mattress after 6 months?
No age milestone makes added softness necessary for infant sleep. Continue using a firm, flat mattress that is designed and approved for the exact crib. Do not add toppers, folded blankets, or extra padding.
Can my baby sleep on their stomach once they can roll?
Always place the baby on their back at the start of sleep. When the baby can roll both ways independently, they generally do not need to be repeatedly repositioned. Keep the sleep space completely clear.
Should I stop room sharing at 6 months?
Six months is the recommended minimum period for room sharing without bed sharing. It is not a required move-out date. Families may continue room sharing when the sleep space remains appropriate and is used according to its instructions.
Do safe-sleep rules apply to naps?
Yes. Back placement, a firm and flat surface, a fitted sheet, and an empty sleep area are recommended for every sleep, including short naps and sleep at another caregiver’s home.
Does a breathing monitor prevent SIDS?
No consumer monitor has been shown to replace safe-sleep practices or prevent SIDS. Use a firm, flat, separate sleep space even when a monitor is being used.
Can SIDS happen after a child turns 1?
The term SIDS applies only to babies younger than 1 year. Other sleep-related injuries can still occur after infancy, so the child’s bed, mattress, bedding, and room should remain appropriate for their age and development.
Use the crib mattress firmness guide to assess support and sagging instead of judging by appearance alone.
Use the flat crib mattress guide to distinguish a level sleep surface from one that sags, tilts, or lifts at the edges.
Separate mattress choices from the room-temperature guidance for infant sleep when managing comfort and overheating.
If the concern is gaps, drafts, or limb movement, review safer alternatives to crib bumpers without lining the sleep space.
