SIDS risk factors: what raises a baby's risk

What SIDS is

NICHD defines SIDS as the sudden death of an infant younger than 1 year of age that remains unexplained after a complete investigation, which can include an autopsy, a review of the death scene, and complete family and medical histories. If no cause is found after that process, the death might be labeled as SIDS (NICHD).

MedlinePlus says SIDS is the leading cause of death in children between one month and one year old, and most SIDS deaths occur when babies are between one month and four months old. Some people call it "crib death" because many babies who die of SIDS are found in their cribs (MedlinePlus). NICHD cites CDC data estimating that about 3,000 infants died from a sudden unexpected infant death in 2022, with more than 1 in 3 of those deaths from SIDS (NICHD).

What causes SIDS

NICHD says the exact cause is not known. Research suggests that many babies who die of SIDS are born with problems in a part of the brain that probably controls breathing, heart rate, blood pressure, temperature and waking from sleep, but that these problems alone may not be enough (NICHD).

Researchers use what NICHD calls the Triple-Risk Model: a baby with an unknown underlying problem, during a key period of development (the first 6 months), meets a stress in the environment such as being placed to sleep on the stomach, overheating, or cigarette smoke. Because the first two cannot be seen ahead of time, NICHD says the most effective way to reduce the risk is to remove or reduce the environmental stresses (NICHD).

What raises the risk

NICHD says factors during pregnancy, at birth and through the first year can affect SIDS risk; many can be changed and some cannot (NICHD).

• Sleep position. Back sleeping carries the lowest risk. Stomach sleeping carries a higher risk, and side sleeping also raises it because babies can easily roll onto their stomach (NICHD). Safe to Sleep says that for a baby who usually sleeps on the back, being put to sleep on the stomach or side, even for a nap, raises the risk of SIDS by up to 45 times (NICHD Safe to Sleep).
• Preterm birth. Babies born before 37 weeks are at higher risk than babies born at full term (NICHD) (see preterm birth risk factors).
• Smoking. Smoking by the mother during pregnancy and smoke around the baby raise the risk (NICHD). Safe to Sleep says smoking during pregnancy greatly increases the risk, and secondhand smoke in the home, the car or other places the baby spends time also increases it (NICHD Safe to Sleep) (see the quit smoking check).
• Drugs and alcohol during pregnancy or by anyone caring for the baby (NICHD Safe to Sleep).
• Overheating, for example from too many layers of clothes and bedding for the room temperature (NICHD Safe to Sleep).
• Soft bedding and objects in the sleep area. Safe to Sleep says research links crib bumpers and any bedding other than a fitted sheet to deaths from SIDS, suffocation, entrapment and strangulation (NICHD Safe to Sleep).
• Age, sex and race. MedlinePlus says premature babies, boys, African Americans, and American Indian/Alaska Native infants have a higher risk (MedlinePlus). NICHD says African American and American Indian/Alaska Native infants are at higher risk than White, Hispanic American, or Asian/Pacific Islander American infants (NICHD).

None of these sources gives a score, and no product can prevent SIDS (NICHD Safe to Sleep).

Sharing a bed

Safe to Sleep says room sharing, with the baby on a separate sleep surface near your bed, is safer than sharing your bed, and that couches and armchairs are never safe places for babies to sleep. It ranks bed sharing as riskier in these situations (NICHD Safe to Sleep):

• Very high risk: a soft surface such as a waterbed, old adult mattress, couch or armchair; an adult who is very tired, taking medicine that causes drowsiness, or using alcohol or other substances; an adult who smokes or uses tobacco, even if not in the bed.
• High risk: a baby younger than 4 months; an adult other than the baby's parent, such as a grandparent or sibling.
• Higher than normal risk: a baby born preterm or at a low birth weight; pillows, blankets or other unsafe items in the sleep area.

Steps that lower the risk

These steps come from NICHD's Safe to Sleep campaign, which bases them on the American Academy of Pediatrics Task Force on SIDS recommendations (NICHD Safe to Sleep):

• Place babies on their backs for every sleep, naps and night, until age 1, including babies born preterm and those with reflux. Once a baby can roll both ways on their own, you can leave them in the position they choose.
• Use a firm, flat, level sleep surface covered only by a fitted sheet, in a crib, bassinet or portable play yard that meets Consumer Product Safety Commission standards. Do not use car seats, strollers, carriers or slings for regular sleep.
• Keep pillows, blankets, quilts, bumpers, toys and other soft or loose items out of the sleep area.
• Share a room, not a bed, for at least the first 6 months.
• Feed the baby human milk, such as by breastfeeding (see the breastfeeding support check).
• Offer a pacifier for naps and at night once feeding is going well; do not attach it to anything or coat it.
• Stay smoke-, vape-, drug- and alcohol-free during pregnancy, and keep the baby's surroundings smoke- and vape-free.
• Avoid overheating: dress the baby for the room, take hats off indoors, and keep the head and face uncovered.
• Get regular prenatal care, and follow the baby's provider's advice on vaccines and checkups. Safe to Sleep says vaccinated babies are at lower risk for SIDS.
• Avoid wedges, positioners, inclined sleepers and other products that claim to prevent SIDS, and do not rely on heart, breathing or motion monitors, which are not effective at detecting or preventing SIDS.
• Stop swaddling once the baby starts to roll over, usually around 3 months; swaddling does not reduce SIDS risk.
• Give plenty of supervised "tummy time" while the baby is awake.

MedlinePlus lists the same core steps: back sleeping, room sharing on a separate infant surface for at least six months, a firm surface with a fitted sheet, no soft objects or loose bedding, breastfeeding, not letting the baby get too hot, and no smoking during pregnancy or near the baby (MedlinePlus).

Related pages

Preterm birth is one of the risk factors NICHD names; see preterm birth risk factors. For help quitting during pregnancy, see the quit smoking check. More pregnancy and newborn guides are on the pregnancy page.

Common questions

Can SIDS be prevented?

NICHD says there is currently no known way to prevent SIDS, but there are ways to reduce the risk; placing the baby on the back for all sleep is one of the most effective (NICHD).

At what age is SIDS most common?

MedlinePlus says most SIDS deaths occur between one month and four months of age (MedlinePlus). SIDS by definition applies to babies younger than 1 year (NICHD).

Do baby monitors prevent SIDS?

No. Safe to Sleep says heart, breathing, motion and similar monitors are not effective at detecting or preventing SIDS (NICHD Safe to Sleep).