SIDS (sudden infant death syndrome) is most likely to occur when a baby is between about 1–4 months old, with a clear peak around 2–3 months of age. The vast majority of SIDS cases (about 90%) happen before 6 months, and risk continues, though much lower, up to 12 months.

Key age windows

  • Highest risk: roughly 1–4 months, especially 2–3 months.
  • Most cases: over 70% of SIDS deaths occur in the first 4 months.
  • Steep decline: after 6 months, cases drop sharply, with more than 90% having already occurred by then.
  • Low but present risk: up to the first birthday, which is why safe sleep guidance is usually recommended until 12 months.

Why this age is riskier

  • In the first 4–6 months, a baby’s brain centers that control breathing and waking from sleep are still maturing, which may make it harder to respond to low oxygen or blocked airways.
  • This same period is when infants spend a lot of time in lighter, more unstable sleep (including REM), which is linked with SIDS vulnerability in research.

Practical reassurance

  • If a baby is past 6 months, the statistical risk of SIDS is much lower than in early infancy, though safe sleep habits should continue until 12 months.
  • Following safe sleep guidelines (back to sleep, firm flat surface, no soft bedding, smoke‑free environment) further reduces risk at any age in the first year.

TL;DR: SIDS is most likely between 1–4 months (peaking at 2–3 months), is rare after 6 months, and even rarer close to 1 year, especially when safe sleep practices are used.

Information gathered from public forums or data available on the internet and portrayed here.