SIDS risk drops dramatically after 6 months of age and is essentially gone by a baby’s first birthday. More than 90% of SIDS deaths occur before 6 months, with the highest concentration between 1 and 4 months, which accounts for 72% of all cases. After 12 months, the diagnosis no longer applies. If an unexplained death occurs in a child older than one year, it falls under a separate category called Sudden Unexplained Death in Childhood (SUDC), which is far rarer.
The Peak Risk Window: 1 to 4 Months
The most dangerous period for SIDS is the first four months of life. Nearly three out of four SIDS deaths happen during this window. The reason traces back to brain development: during the transition from life in the womb to life outside it, the parts of the brainstem responsible for breathing, heart rate, blood pressure, and waking from sleep are still maturing rapidly. This immaturity makes young infants more vulnerable.
Specifically, the brain’s ability to sense rising carbon dioxide levels and respond by adjusting breathing is underdeveloped in the earliest weeks and months. So is the arousal response, the mechanism that wakes a baby when breathing is compromised, such as when their face is pressed into a soft surface. In healthy development, these systems strengthen steadily through the first half-year of life, which is why risk falls so sharply after that point.
How Risk Changes From 6 to 12 Months
After 6 months, SIDS becomes uncommon but not impossible. The remaining roughly 10% of cases are spread across months 7 through 12. By this age, most babies have stronger arousal responses, better head and neck control, and the ability to roll freely in both directions. These physical milestones make it much harder for a baby to become trapped in a position that restricts airflow.
That said, the American Academy of Pediatrics recommends continuing safe sleep practices through the entire first year. Certain risk factors also remain relevant in the second half of infancy: premature birth, low birth weight, exposure to cigarette smoke, and having a sibling who died of SIDS all elevate risk regardless of age within that first year.
Why Rolling Over Is a Turning Point
One of the milestones parents watch most closely is rolling. Babies may begin rolling as early as 2 months, though most develop the skill between 4 and 6 months. Once your baby can roll from back to stomach and from stomach to back on their own, you can let them stay in whatever position they choose after you place them on their back to start sleep. If they can only roll one way, reposition them onto their back if they end up on their stomach.
Rolling ability matters because it signals that a baby has enough muscle strength and neurological coordination to move their head and body away from a suffocation hazard. This is also the point when swaddling needs to stop. A swaddled baby who rolls onto their stomach cannot use their arms to push up or reposition, which creates a suffocation risk.
Safe Sleep Guidelines for the Full First Year
The AAP’s 2022 recommendations apply to the entire first 12 months. The core practices are straightforward: place your baby on their back for every sleep, use a firm and flat mattress with only a fitted sheet, and keep the crib free of pillows, blankets, stuffed animals, and bumper pads. Room sharing (not bed sharing) is recommended for at least the first 6 months.
Instead of blankets, dress your baby in layers or use a wearable blanket to keep them warm. Weighted blankets, weighted swaddles, and weighted sleepers should not be used at any age during the first year. These guidelines remain in place even after the highest-risk months have passed because suffocation and entrapment, while distinct from SIDS, are part of the broader category of sudden unexpected infant deaths. In 2022, roughly 3,700 babies in the United States died from all sudden unexpected causes combined, including 1,529 from SIDS specifically.
Protective Habits That Help Most Early On
Offering a pacifier at the onset of sleep is one of the simplest protective measures. The AAP recommends introducing a pacifier at bedtime starting at one month of age (or once breastfeeding is well established). The protective benefit is strongest during the first six months. Breastfeeding also reduces SIDS risk, with longer duration offering greater protection.
These measures matter most during the 1 to 4 month peak, when a baby’s own protective reflexes are least developed. As the brain matures and your baby gains the ability to wake themselves, move freely, and regulate breathing more reliably, the biological vulnerability that defines SIDS gradually resolves. By the first birthday, the risk period is over.