Sudden infant death (often called cot death or SIDS) does not have a single known cause; experts think it happens when several risk factors come together in a vulnerable baby during sleep. The focus today is on understanding these risks and reducing them as much as possible.

What cot death is

  • Cot death (sudden infant death syndrome, SIDS) is the sudden, unexpected death of an apparently healthy baby during sleep, usually under 1 year of age.
  • It most often happens between 2 and 4 months, but can occur any time in the first year.

What seems to cause it

Researchers talk about a “triple risk”: a vulnerable baby, a critical stage of development, and a stress or trigger in the sleep environment.

Key factors thought to be involved include:

  • Baby vulnerability
    • Premature birth or low birth weight, which can affect how well the brain controls breathing, heart rate and temperature.
* Subtle brainstem differences that may reduce a baby’s ability to wake or respond to low oxygen or overheating.
  • Environmental triggers during sleep
    • Sleeping on the tummy or side rather than on the back, which is linked to greatly increased SIDS risk.
* Soft bedding, pillows, quilts, cot bumpers, or loose blankets that can cover the face or cause rebreathing of exhaled air.

* Overheating from too many layers, heavy blankets, or a very warm room.

* Head covering (blankets or hoods over the head) during sleep.
  • Smoke and substances
    • Maternal smoking in pregnancy is one of the strongest known risk factors and may explain a large proportion of cases in some studies.
* Second-hand smoke after birth, even if not in the bedroom, also significantly raises risk.

* Alcohol or drug use by caregivers, especially when bed-sharing, increases the chance of accidental suffocation or unsafe sleeping situations.
  • Sleep setting and bed-sharing
    • Bed-sharing with adults, especially on sofas or armchairs, is linked with more deaths, often from accidental suffocation or overlaying.
* Sleeping on very soft surfaces like sofas, waterbeds, or adult mattresses with heavy duvets is unsafe for infants.

Things that are NOT proven causes

  • No single “toxic mattress chemical” has been shown to be a proven cause, and expert reviews have rejected earlier toxic gas theories about fire retardants in mattresses.
  • Many infections (like common colds) occur around SIDS, but no single germ has been confirmed as the cause, although bacteria such as Staphylococcus aureus and E. coli are being studied.

How parents can reduce the risk

While SIDS cannot be completely prevented, certain habits greatly lower the risk.

  • Safe sleep position and place
    • Always place baby on the back to sleep for every sleep, day and night.
* Use a firm, flat mattress with a fitted sheet; keep the cot clear of pillows, bumpers, soft toys and loose bedding.

* Let baby sleep in the same room as parents (but on a separate, safe sleep surface) for at least the first 6 months.
  • Avoid smoke and substances
    • Do not smoke during pregnancy or after birth, and keep the home and car completely smoke-free.
* Avoid bed-sharing if anyone has smoked, taken drugs, or drunk alcohol, or if the baby is premature or low birth weight.
  • Temperature and clothing
    • Keep the room comfortably cool, not hot, and dress baby in light sleep clothing with lightweight covers if needed.
* Make sure baby’s head is not covered by blankets or hats indoors.
  • Feeding and routine care
    • Breastfeeding is associated with a lower risk of SIDS.
* Offering a dummy (pacifier) at sleep times may reduce risk, though parents should balance this with breastfeeding plans and local advice.

Emotional and support aspect

  • Many parents never get a clear “why,” even after investigation, because SIDS is usually a combination of subtle vulnerabilities and circumstances rather than a single cause.
  • Specialist charities and bereavement services exist in many countries to support families affected by cot death, offering both practical information and emotional support.

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