In the United States, SIDS causes about 42 deaths per 100,000 live births each year. That translates to roughly 1,529 infant deaths from SIDS in 2022, making it relatively rare but still the leading cause of death in infants between one month and one year of age. The rate has dropped dramatically since the early 1990s, largely due to the “Back to Sleep” campaign that encouraged placing babies on their backs.
SIDS vs. SUID: Why the Numbers Can Be Confusing
When you search for SIDS statistics, you’ll often see a larger number: about 3,700 sudden unexpected infant deaths (SUID) per year. That’s because SUID is the broader category. It includes SIDS, accidental suffocation and strangulation in a sleep environment, and other unexplained infant deaths. SIDS specifically refers to cases where no cause of death can be identified even after a thorough investigation. So of those 3,700 total sudden infant deaths in 2022, 1,529 were classified as SIDS, with the remainder attributed to suffocation or left unexplained for other reasons.
When the Risk Is Highest
SIDS can happen at any point during a baby’s first year, but the risk is heavily concentrated in the early months. More than 90% of all SIDS deaths occur before six months of age, and 72% happen between months one and four. The first few weeks of life and the period after six months carry comparatively lower risk, though they are not zero-risk periods.
How Rates Have Changed Over Time
The SIDS rate in the early 1990s was far higher than it is today. The introduction of safe sleep campaigns, particularly the recommendation to place babies on their backs, led to a steep decline through the late 1990s. That decline eventually leveled off, and the overall SUID rate has remained relatively stable in recent years at around 101 deaths per 100,000 live births. Within that total, SIDS-specific deaths have continued a gradual downward trend, though some of that shift reflects changes in how deaths are classified rather than a true reduction in unexplained infant deaths.
Racial and Ethnic Disparities
SIDS does not affect all communities equally. American Indian and Alaska Native infants face a SIDS rate that is 95% higher than that of non-Hispanic white infants (78.3 vs. 40.1 deaths per 100,000 live births). Non-Hispanic Black infants face an 83% higher rate (73.3 per 100,000). These disparities are driven by a combination of factors including differences in access to prenatal care, housing conditions that make safe sleep setups harder to maintain, and higher rates of other known risk factors like smoking.
What Increases the Risk
Smoking during pregnancy is one of the strongest modifiable risk factors. Infants whose mothers smoked while pregnant are nearly four times more likely to die of SIDS, and that risk climbs with the number of cigarettes smoked per day. Mothers who smoked more than a pack a day during pregnancy had over five times the risk compared to nonsmokers. Smoking after birth also raises the risk, roughly 2.5 times, likely because of secondhand smoke exposure during sleep.
Bed sharing is another significant factor. For babies under three months old, sharing a bed with a parent raises the risk roughly fivefold compared to sleeping in a separate crib or bassinet in the same room, even when parents don’t smoke. For babies of all ages, the overall risk increase from bed sharing is about 2.7 times. Room sharing without bed sharing, by contrast, is considered protective.
Other factors linked to higher risk include premature birth, low birth weight, sleeping on the stomach or side, soft bedding or loose blankets in the sleep space, and overheating.
Safe Sleep Guidelines
The American Academy of Pediatrics recommends a straightforward set of practices that address the major risk factors:
- Back sleeping: Place infants on their backs for every sleep, including naps.
- Firm, flat surface: Use a crib, bassinet, or portable play yard with a firm mattress and fitted sheet. Nothing else in the sleep space.
- Own sleep area: Babies should sleep in the same room as a caregiver but not in the same bed, and never on a couch, armchair, or swing.
- No soft items: Keep pillows, stuffed animals, bumper pads, and loose blankets out of the crib.
- Breastfeed if possible: Breastfeeding is associated with lower SIDS risk.
- Smoke-free environment: Avoid smoking during pregnancy and keep the baby’s environment free of tobacco smoke.
A Possible Biological Clue
A 2022 study published in eBioMedicine found that babies who later died of SIDS had lower levels of a specific enzyme involved in nervous system signaling, measured from blood samples taken two to three days after birth. The 26 SIDS cases in the study had significantly lower enzyme activity compared to 254 matched controls, while babies who died of other sudden causes did not show this difference. This suggests some infants may have a biological vulnerability that makes them less able to rouse themselves from dangerous sleep situations like low oxygen. The study was small and the finding hasn’t yet led to a screening test, but it represents the first measurable biological difference identified at birth between babies who go on to die of SIDS and those who don’t.