What is SIDS, SUDC, & Stillbirth?

What is SIDS?

SIDS (Sudden Infant Death Syndrome) is the sudden, unexpected death of an apparently healthy infant under the age of one year which remains unexplained, even after the performance of a complete autopsy and other associated tests, examination of the death scene and a review of the clinical history. SIDS seems to occur during a phase of sleep.

SIDS is a recognized medical diagnosis in the International Classification of Diseases, (9th Revision). SIDS is a diagnosis of exclusion. It is a name given when all known causes of death have been ruled out. SIDS is not related to accidental suffocation. It is related to underlying vulnerabilities in the infant not yet understood by science.

What are SUID and SUDI?

Sudden Unexpected Infant Death (SUID) and Sudden Unexpected Death in Infancy (SUDI) refer to the death of an infant younger than one year of age that occurs suddenly and unexpectedly, but for which a cause of death can be identified  after full investigation.

What is SUDC

Sudden Unexplained Death in Childhood (SUDC) is the death of a child over the age of 12 months which remains unexplained after a thorough investigation and autopsy. As with SIDS, SUDC is a diagnosis of exclusion given when all known and possible causes of death have been ruled out. For more information on SUDC, visit the SUDC Foundation.

What Causes SIDS?


We do not know the cause or causes of SIDS. At this time, SIDS is neither predictable nor preventable.

Many researchers think that SIDS is not a single disease but rather is a result of multiple interacting factors. Current advances in medicine indicate that an underlying abnormality due to genetic, biologic or molecular disorders may be responsible for a large proportion of sudden infant deaths. At present genetic and molecular testing are not yet part of routine sudden infant death investigations carried out by the coroners or medical examiners. Restricted access to tissues from SIDs victims and limited funding for research continue to be major obstacles for progress.

Infants Affected

SIDS is the leading cause of death in infancy between one and twelve months of age, with the majority of deaths occurring between 2-4 months. Ninety percent of SIDS deaths occur in the first six months. SIDS occurs throughout the world in all cultures.

There is no way to tell at this time which babies are at risk of sudden death. SIDS can occur in very strong, healthy looking children. The majority of these babies are well nourished, well cared for, and in apparent good health prior to death.

Risk Reduction

While risk reduction strategies, including safe sleep practices, have helped lower the rate of SIDS in recent years, they cannot alone prevent SIDS. Risk factors are not causes. SIDS can happen to babies with known risk factors, as well as babies who have no known risk factors. It can still occur even when families and caregivers follow all recommended risk reduction strategies.

The only way that we will one day be able to prevent SIDS deaths is by finding, understanding and treating the underlying biological causes of SIDS.

Separating Facts from Fiction

  • SIDS cannot be predicted or prevented at this time.
  • SIDS is not caused by neglect or child abuse.
  • SIDS occurs quickly and quietly, usually during a particular phase of sleep.
  • SIDS is not caused by vomiting or choking.
  • SIDS is not the same as accidental suffocation.
  • SIDS is not contagious or infectious.
  • SIDS is not caused by vaccinations or by toxic gases.
  • SIDS has been around for many generations.
  • SIDS has underlying biological causes and is felt to be a medical disorder.
  • SIDS is thought to have more that one cause, although the introduction of new research may show one main cause with multiple factors underlining its complexity.
  • SIDS is not anyone’s fault.

What is Stillbirth?

Stillbirth is the birth of a baby who is born without any signs of life at or after 20 weeks pregnancy or weighing more than 500g. The baby may have died during pregnancy (called intrauterine death), labour or birth.

What causes a baby to be stillborn?

Stillbirth causes can greatly vary and they are not always identifiable. However, we do know of some factors that may lead to stillbirth:

  • A baby did not grow enough in the uterus.
  • A genetic or physical defect in the baby. This means the baby’s brain, heart or other organ has not developed properly.
  • Heavy bleeding after 24 weeks of pregnancy. This can happen when the placenta begins to separate from the lining of the uterus. It is called a placental abruption.
  • Pre-eclampsia, which can reduce blood flow to the baby via the placenta. This condition is associated with placental abruption.
  • An illness suffered by the mom, such as diabetes, the liver condition obstetric cholestasis, or a blood-clotting problem.
  • A problem with the way the baby is born. A baby’s shoulders may get stuck as he/she the birth canal (shoulder dystocia), severely reducing oxygen flow to the baby.
  • Infections, such as listeriosis, salmonella or toxoplasmosis.

Infants Affected

In the Canada, just over 4.5 in 1000 births ends in stillbirth.