SIDS risk drops dramatically after 6 months of age and is essentially over by a baby’s first birthday. More than 90% of all SIDS deaths occur before 6 months, with the highest concentration between 1 and 4 months. After 8 months, SIDS becomes uncommon, and the medical definition of SIDS only applies to infants under 1 year old. That said, safe sleep practices are recommended through the entire first year.
The Peak Risk Window: 1 to 4 Months
The most dangerous period is narrower than many parents realize. Seventy-two percent of all SIDS deaths happen between months 1 and 4. Newborns in the first few weeks have some risk, but it climbs quickly and peaks around 2 to 4 months before starting to decline. By the time a baby reaches 6 months, over 90% of the total SIDS risk has already passed.
After 8 months, SIDS is rare. The National Institutes of Health notes that while SIDS can technically occur anytime in the first year, cases past 8 months are uncommon enough that the focus shifts from SIDS specifically to general sleep safety. In 2022, there were approximately 1,529 SIDS deaths in the United States, all among infants under 1 year old.
Why the Risk Peaks and Then Fades
The 2-to-4-month danger zone lines up with a critical phase of brain development. During this window, the parts of the brainstem responsible for breathing control and arousal from sleep are undergoing major changes. Normally, when a baby’s oxygen drops or carbon dioxide rises during sleep, they respond automatically: sighing, turning their head, thrashing, or crying to wake themselves up and restore normal breathing. In babies vulnerable to SIDS, this protective wakeup response appears to be impaired or delayed in maturing.
Studies of infants who were on monitors before they died of SIDS showed they had fewer spontaneous arousals during sleep, altered sleep patterns, and more episodes of obstructed breathing compared to other infants. Essentially, their brains weren’t sending the alarm signal strongly enough when breathing became compromised.
As babies grow past this critical window, their respiratory control systems become more robust. The balance of brain chemicals shifts from inhibitory signals toward excitatory ones, meaning the brain gets better at jolting awake when something goes wrong. By 6 months, most infants have a much more mature arousal response, which is a major reason the risk drops so sharply.
How Rolling Over Changes the Picture
Physical milestones also play a protective role. Babies who can roll in both directions, from back to front and front to back, have the strength and coordination to reposition themselves if they end up face-down during sleep. This ability typically develops between 4 and 6 months, overlapping with the period when SIDS risk is declining.
If your baby can only roll one way (say, back to tummy but not back again), you should gently reposition them onto their back whenever you notice they’ve flipped. Once they can roll confidently in both directions without help, you can continue placing them on their back at bedtime but let them find their own sleeping position overnight. There’s no need to wake up repeatedly to flip them back.
Safe Sleep Practices Through the First Year
Even though the sharpest risk is behind you by 6 months, pediatric guidelines recommend maintaining safe sleep habits until your baby turns 1. That means a firm, flat sleep surface with no pillows, blankets, stuffed animals, or bumper pads in the crib. Use a wearable blanket or sleep sack instead of loose bedding, or dress your baby in layers for warmth.
The American Academy of Pediatrics recommends room sharing (sleeping in the same room but on separate surfaces) for at least the first 6 months, and ideally through the first year. Sleep-related death rates are highest in the first 6 months, making room sharing especially important during that stretch. There’s no specific evidence establishing when it becomes safe to move a baby to their own room before 12 months, so the guidance stays consistent through the full year.
Two environmental factors remain relevant throughout infancy. Overheating can interfere with breathing regulation and arousal, so keeping the room at a comfortable temperature and avoiding heavy layers matters at every age. Secondhand smoke exposure also raises risk. Babies living with smokers face higher rates of SIDS, and the risk increases with more smokers in the household and more time spent in smoke-filled environments.
After Age 1: A Different Category
Once your child passes their first birthday, SIDS is no longer the applicable diagnosis. Sudden, unexplained deaths in children older than 1 are classified separately as Sudden Unexplained Death in Childhood, or SUDC. This is an extremely rare condition, far less common than SIDS, and it was formally defined in 2005 to fill a gap left when SIDS was restricted to infants under 1 year.
The first birthday is also the milestone when most safety organizations consider it acceptable to introduce soft bedding like a small pillow or light blanket. Before that point, these items pose a suffocation risk that outweighs any comfort benefit. After 12 months, your child’s motor skills, strength, and neurological maturity make the sleep environment far less hazardous than it was during those early months.