Sudden Infant Death Syndrome (SIDS) refers to the sudden and unexplained death of an infant younger than one year of age. This diagnosis is made only after a thorough investigation, including a death scene examination, a complete autopsy, and a review of the clinical history, fails to identify a specific cause of death. SIDS is therefore considered a diagnosis of exclusion, meaning other potential causes of death must be ruled out before SIDS is confirmed. Parents often seek to understand the duration of this risk during their baby’s first year.
Understanding the SIDS Risk Window
The risk of SIDS is present throughout an infant’s first year, but it is not uniformly distributed. The most vulnerable time for SIDS is typically between one and four months of age, representing the peak risk period. During these months, approximately 72% of SIDS deaths occur.
The majority of SIDS cases, over 90%, happen before a baby reaches six months old. After six months, the risk of SIDS begins to significantly decrease. While SIDS is less common after eight months of age, it is important to continue safe sleep practices until a baby’s first birthday.
Key Risk Factors
Several factors can increase an infant’s susceptibility to SIDS. Babies born prematurely or with a low birth weight face a higher risk, as their brain development, particularly in areas controlling breathing and arousal from sleep, may not be fully mature. Boys are also slightly more likely to be affected than girls. A baby’s recent health can also play a role, with some infants who died from SIDS having experienced a recent respiratory infection. Maternal health and behaviors during pregnancy also contribute to risk; mothers who are younger than 20, smoke, use drugs or alcohol, or receive inadequate prenatal care may have babies with an increased SIDS risk. A family history of SIDS in a sibling also slightly elevates the risk.
Proven Strategies for Risk Reduction
Evidence-based strategies can significantly reduce the risk of SIDS. These recommendations are often summarized as the “ABC’s of safe sleep”: Alone, Back, Crib. Infants should always be placed on their back to sleep for all sleep times, including naps, until they are one year old.
A safe sleep environment means placing the baby in a crib, bassinet, or play yard with a firm, flat mattress covered only by a fitted sheet. Keep the sleep area clear of soft objects such as blankets, pillows, bumper pads, stuffed animals, and toys, as these can pose suffocation hazards.
Other important measures include:
Room-sharing, with the baby in a separate sleep space in the parents’ room, for at least the first six months, and ideally the first year. Bed-sharing is not advised.
Avoiding overheating by dressing babies lightly for sleep and keeping the room temperature comfortable (typically between 16 and 20°C).
Offering a pacifier at sleep times, once breastfeeding is well established.
Staying up-to-date with routine childhood immunizations and breastfeeding whenever possible.
Beyond the Peak Risk: When Concern Lessens
While SIDS can occur at any point during the first year, the risk becomes extremely low after a baby’s first birthday. As infants grow and develop, their neurological systems mature, which includes improved control over breathing and arousal mechanisms during sleep. This developmental progress contributes to the significant reduction in SIDS risk as they approach and pass their first year.
Although the specific concern for SIDS diminishes considerably after 12 months, continuing safe sleep practices is still beneficial for general infant safety.