What is SIDS ?

Latest update: October 3, 2020

Author Name: Heidi Holvoet, PhD
Medical fact-check: Dr Leah Alexander, M.D., F.A.A.P.

SIDS, or Sudden Infant Death Syndrome, is when a baby dies suddenly with no obvious signs of illness or any other possible cause. It is the most cruel and frightening thing that can happen to a newborn and her family.

Cot death and crib death are two common terms used to refer to the same syndrome, although SIDS can and does also occur on the sofa or in a play pen.

To parents of SIDS babies

My thoughts are with you constantly while writing these pages. Please accept my sincere condolences and warm thoughts for you and your little angel.

These pages are written for information purposes, to help increase awareness and point at measures towards reducing the risk of SIDS.

If any content here makes you feel uneasy or is inappropriate in any way, I apologize. Please let me know through the contact form so I can make the necessary changes.

If you are looking for support, you can also contact me. For specialized support, allow me to refer you to your local SIDS organization. You can find it through the International Society for the Study and Prevention of Infant Death ISPID.org (opens in new window).

Sadly enough, the What is SIDS? question does not have simple or clear answers. The syndrome remains a mystery in many aspects: there is no single cause or risk factor associated with it.

It is a so-called diagnosis of exclusion. This means that when a young baby dies and no cause is found, Sudden Infant Death Syndrome is used as a label.

A lot of research has been done and is done today.

Much of the medical literature about SIDS mentions infant brain immaturity or an “undetected defect” that impairs breathing during sleep, see for example this article and here.

Even if SIDS has not disappeared completely, numbers have decreased in the past 2-3 decades.

This decrease is largely attributed to campaigns by governments world wide to make parents aware of the possible risk and how to reduce this risk.

SIDS risk factors

Research has deduced higher-risk factors from studying affected babies and their families worldwide.

Babies with one or more of these have an increased risk of being affected by Sudden Infant Death Syndrome.

A baby may be at higher risk if she:

  • was born prematurely
  • had a low birth weight
  • was subject to passive smoking (due to smoking by mother or others around during pregnancy and after birth)

or if mom:

  • was overweight during pregnancy
  • is a teen mother
  • was drinking alcohol during pregnancy

There's no need to panic if any of this factors apply to your situation, but you may need to pay extra attention to certain precautions and, in any case, consult a medical professional.

Remember that all babies can be victims. Whether your child has none of these risk factors or several, it is ALWAYS important to follow the prevention guidelines.


About SIDS and Statistics

What is SIDS? With many uncertainties remaining, one often talks about SIDS in terms of numbers, statistics. This sounds awful since one is actually talking about real babies and their families, who should never be treated as numbers.

But statistics do allow science to study SIDS and to try and reveal as many risk factors and risk reduction guidelines as possible.

Numbers often vary by country, not only because of different cultures and habits, but also because of the way each country defines and collects numbers.

Only numbers of general interest are included here. Although these numbers have been selected with the utmost care, please view them for what they are: average numbers that give a general idea about the topic.

SIDS affects babies of all countries, cultures, and backgrounds, but the incidence is higher among Black and Native Americans as is also detailed in this peer-reviewed article.

The peak risk age is between 2 and 4 months old. In principle SIDS occurs from 1 month up to 1 year old, with very rare cases at higher and lower ages.

More baby boys are affected than girls.

Each year, worldwide, about 1 in 1000 babies die and are diagnosed with SIDS. In some countries this number went down to 1 in 10 000 babies in the past decades.[1],[2]


[1] International trends in sudden infant death syndrome Hauck RF, Tanabe KO. 2008.  Pediatrics 122(3): 660-666.

[2] Supplemental analyses of recent trends in infant mortality Kochanek, KD, Martin, JA. Reviewed October 15, 2008. Hyattsville, Maryland: National Center for Health Statistics. Available at http://www.cdc.gov/nchs/products/pubs/pubd/hestats/infantmort/infantmort.htm (opens in new window)