[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Conditions](https://durgical.com/en/conditions/) › Sudden infant death syndrome (SIDS)

[Conditions](https://durgical.com/en/conditions/) · [Pediatrics and neonatology](https://durgical.com/en/conditions/)

# Sudden infant death syndrome (SIDS)

SIDS is the sudden, unexplained death of a healthy-seeming baby under one year, usually during sleep. Safe sleep on the back lowers the risk.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Medulla oblongata](https://durgical.com/en/anatomy/medulla-oblongata/)
- [Pons](https://durgical.com/en/anatomy/pons/)
- [Trachea](https://durgical.com/en/anatomy/trachea/)

## In embryology

- [Ionizing radiation, tobacco and cocaine](https://durgical.com/en/embryology/ionizing-radiation-tobacco-and-cocaine/)

## Why it happens

- [Sudden infant death syndrome: what is known](https://durgical.com/en/general-pathology/sudden-infant-death-syndrome-what-is-known/)
- [The autopsy: clinical and medicolegal](https://durgical.com/en/general-pathology/the-autopsy-clinical-and-medicolegal/)
- [Control of breathing, chemoreceptors and lung reflexes](https://durgical.com/en/physiology/control-of-breathing-chemoreceptors-and-lung-reflexes/)

## What it is

The sudden death of an infant under 1 year of age, usually during sleep, that remains unexplained after a full investigation including autopsy, review of the death scene and the clinical history. It is part of the wider group of sudden unexpected infant deaths.

## Who gets it

A leading cause of death between 1 month and 1 year of age, with a peak at 2–4 months; about 90% occur before 6 months. Rates fell sharply worldwide after back-to-sleep campaigns. In Colombia and Latin America, bed-sharing, prone sleeping and smoke exposure remain common risks, and many sudden deaths are not certified as SIDS, so the true rate is uncertain.

## Causes

- Unknown; best explained by a triple-risk model: a vulnerable infant, a critical developmental period and an external stressor
- Abnormal brainstem (medullary serotonergic) control of breathing, arousal and heart rate in some infants

## Risk factors

- Prone (face-down) or side sleeping
- Soft surfaces, loose bedding, pillows or toys in the sleep space
- Bed-sharing, especially with a smoker, an adult under alcohol or sedative effect, or on a sofa
- Maternal smoking in pregnancy and smoke exposure after birth
- Prematurity and low birth weight; male sex
- Overheating and overwrapping
- Young maternal age and little prenatal care

## Pathophysiology

In a vulnerable infant, an external stressor such as face-down sleeping or covering of the face leads to rebreathing of exhaled air, hypoxia and hypercapnia. A normal infant would wake and turn the head; in SIDS, immature or abnormal brainstem arousal and cardiorespiratory reflexes fail, leading to apnoea, bradycardia and death.

## Symptoms and signs

- No warning signs: a previously well-appearing infant is found dead or unresponsive, usually after being put down to sleep
- Autopsy shows no explanatory cause; petechiae on the thoracic organs may be found

## Red flags

- Injuries, fractures, retinal haemorrhages or an inconsistent history at autopsy, which point to maltreatment rather than SIDS
- A brief resolved unexplained event (BRUE) with high-risk features
- A previous unexplained infant death in the same family

## Diagnosis

**Clinical**
A diagnosis of exclusion made after death: full autopsy, a death-scene investigation and review of the medical and family history. Clinicians apply a standard protocol for any sudden unexpected infant death, which includes forensic notification.

**Tests**
Post-mortem toxicology, microbiology, metabolic screening (e.g. fatty-acid oxidation disorders) and, when relevant, genetic testing for cardiac channelopathies.

**Imaging**
Post-mortem skeletal survey to exclude fractures; CT or MRI may support the autopsy.

## Differential diagnosis

- Accidental suffocation or strangulation in bed
- Abusive injury, including abusive head trauma or smothering
- Overwhelming infection (sepsis, meningitis, myocarditis)
- Inborn errors of metabolism
- Cardiac arrhythmias such as long QT syndrome

## Goal of treatment

There is no treatment once it has happened; the aim is prevention through safe-sleep education, plus compassionate support for the family and a full, non-judgemental investigation.

## Treatment

**Acute**
Resuscitation is attempted when the infant is found unresponsive, following paediatric life-support protocols.

**Lifestyle**
Safe-sleep counselling for every family (an NCLEX nursing priority): baby on the back for every sleep, a firm flat separate surface, room-sharing without bed-sharing, no soft objects, no smoke exposure, avoid overheating.

**Follow-up**
Bereavement support, grief counselling and follow-up for the family; home cardiorespiratory monitors are not recommended as a SIDS prevention strategy.

## Complications

- Intense parental grief, guilt and depression
- Anxiety in later pregnancies and with siblings

## Prognosis

Fatal by definition. Risk falls substantially with safe-sleep practices, breastfeeding and a smoke-free environment, and becomes very low after the first year.

## Prevention

- Back to sleep for every sleep, including naps; supervised tummy time while awake
- Firm, flat mattress with a fitted sheet and no pillows, bumpers, blankets or toys
- Room-sharing on a separate surface for at least the first 6 months; avoid sofas and adult beds
- Breastfeeding and complete immunisation
- No smoking in pregnancy or around the baby; no alcohol or sedatives in caregivers who share a room
- Avoid overheating; consider a pacifier at sleep time

## Test yourself

Think of the answer, then tap the question to see it.

## At what age does SIDS peak?

Between 2 and 4 months of age; most cases occur before 6 months.

## What is the single most important safe-sleep recommendation to reduce SIDS?

Placing the infant on the back (supine) for every sleep.

## Why is SIDS called a diagnosis of exclusion?

It is made only after autopsy, death-scene investigation and history review find no other cause.

## Which brain region is implicated in SIDS research?

The brainstem (medulla), with abnormal serotonergic control of breathing and arousal.

## What are three modifiable risk factors for SIDS?

Prone sleeping, soft bedding or bed-sharing, and tobacco smoke exposure (also overheating).

[Add to my cards (5)](https://durgical.app/estudiar/?add=/en/conditions/sudden-infant-death-syndrome/)

## Related conditions

- [Child maltreatment (physical abuse, abusive head trauma, neglect)](https://durgical.com/en/conditions/child-maltreatment/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Sudden Infant Death Syndrome](https://medlineplus.gov/suddeninfantdeathsyndrome.html) (MedlinePlus, US National Library of Medicine, 2026).

[← All conditions](https://durgical.com/en/conditions/)

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

---
Source: https://durgical.com/en/conditions/sudden-infant-death-syndrome/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/sudden-infant-death-syndrome/