SIDS (Sudden Infant Death Syndrome)

Sudden infant death syndrome (SIDS) — commonly known as cot death — is, according to the NHS, "the sudden and unexplained death of an apparently healthy baby aged up to 12 months old." The Lullaby Trust defines it as "the sudden and unexpected death of a baby where no cause is found." Despite decades of research, the exact mechanism remains unknown. There is no evidence that babies who die from SIDS show prior symptoms.

When is the risk highest?

The Lullaby Trust reports that approximately nine out of ten SIDS deaths (around 87%) occur when babies are six months old or younger, with the most vulnerable period being under three months of age. Safer sleep guidance is recommended for all sleep periods until a baby reaches 12 months.

What factors are associated with increased risk?

Both the NHS and The Lullaby Trust identify several factors associated with higher SIDS risk: exposure to cigarette smoke during pregnancy or after birth; prematurity (birth before 37 weeks) or low birth weight (under 2.5 kg); overheating during sleep; sleeping on a surface other than a firm, flat mattress; co-sleeping on a sofa or armchair; and co-sleeping with a caregiver who smokes, has consumed alcohol, or is taking sedating medication.

What does the evidence say about prevention?

The Lullaby Trust states that its safer sleep advice "has saved the lives of over 31,951 babies since 1991." Key evidence-based measures include always placing babies on their back to sleep, room-sharing for at least the first six months, maintaining a smoke-free environment, keeping the cot clear of pillows, duvets, bumpers, and toys, and maintaining a room temperature of 16–20°C. The Lullaby Trust also notes that "any amount of breastfeeding reduces the risk of sudden infant death syndrome."