UNSW Embryology

Abnormal Development - Sudden Infant Death Syndrome

© Dr Mark Hill (2009)

Acknowledgements

Introduction

Sudden Infant Death Syndrome (SIDS) ("cot death" or "crib death") is a term used to describe the sudden, unexplained death of an infant younger than one year old. The specific causes of SIDS are still unknown but there are known ways to reduce the risk (More? Risk Reduction). Some research points to exposure to familial disorders, smoking (pasive smoking) and defects of fat metabolism as potential additional risk factor. There is also current scientific discussion concerning the potential role of serotonin abnormalities in the brain stem.

In the United Kngdom, it was not until 1971 that sudden infant death syndrome or any of its synonyms was accepted by the registrar general as a cause of death.

Page Links: Introduction | Some Recent Findings | Risk Reduction | NHMRC-SIDS Publication |Smoking and Pregnancy | References | WWW Links | Glossary

Related Pages: Abnormal Development- Smoking

Some Recent Findings

Sudden infant death syndrome and prone sleeping position. Dwyer T, Ponsonby AL. Ann Epidemiol. 2009 Apr;19(4):245-9. PMID: 19344862

"What we have learned since 1990 is that the prone sleep position was a major component of a casual pathway that was operating in over half of the SIDS deaths that were occurring in developed countries at the end of the 1980. It has been estimated that advice to place infants supine to sleep may have saved in the order of 850 infants annually in Australia and other countries."

Serotoninergic receptor 1A in the sudden infant death syndrome brainstem medulla and associations with clinical risk factors. Machaalani R, Say M, Waters KA. Acta Neuropathol. 2009 Mar;117(3):257-65. Epub 2008 Dec 4. PMID: 19052756

"We hypothesized that immunoreactivity of 5HT(1A)R would be reduced in infants diagnosed with sudden infant death syndrome (SIDS). In particular that those infants with known clinical risk factors (including cigarette smoke exposure, bed sharing and sleep position) would have greater changes than those without clinical risks. Comparing SIDS (n = 67) to infants who died suddenly with another diagnosis (non-SIDS, n = 25), we found decreased 5HT(1A)R immunoreactivity in the majority of the nuclei studied at the rostral medulla level including dorsal motor nucleus of the vagus (DMNV), nucleus of the solitary tract, vestibular, and inferior olivary nucleus (ION). There was a significant relationship with all risk factors for 5HT(1A)R, especially for DMNV, suggesting that 5HT(1A)Rs are highly vulnerable to various insults within the SIDS DMNV. This study not only provides further evidence of abnormalities within the brainstem serotoninergic system of SIDS infants, but also shows that these changes may be associated with exposure to clinical risk factors."

Risk Reduction

• Placing babies on their backs to sleep, even for short naps
  • "tummy time" is for when babies are awake and someone is watching
• Using a firm sleep surface
  • such as a crib mattress covered with a fitted sheet
• Keeping soft objects and loose bedding away from sleep area
• Making sure babies don't get too hot
  • keep the room at a comfortable temperature for an adult

(Source: National Institute of Child Health and Human Development)

Smoking and Pregnancy

• Smoking doubles the risk of having a low-birthweight baby and significantly increases the rate of perinatal mortality and several other adverse pregnancy outcomes.
• The mean reduction in birthweight for babies of smoking mothers is 200 g.
• High quality interventions to help pregnant women quit smoking produce an absolute difference of 8.1% in validated late-pregnancy quit rates.
• If abstinence is not achievable, it is likely that a 50% reduction in smoking would be the minimum necessary to benefit the health of mother and baby.
• Healthcare providers perform poorly in antenatal interventions to stop women smoking. Midwives deliver interventions at a higher rate than doctors.
• The efficacy of nicotine replacement therapy has not been established in pregnancy. Currently, its use should only be considered in women smoking more than 10 cigarettes per day who have made a recent, unsuccessful attempt to quit and who are motivated to quit.
• Relapse prevention programs have shown little success in the postpartum period.

Data from: Quitting smoking in pregnancy Raoul A Walsh, John B Lowe, Peter J Hopkins (MJA 2001; 175: 320-323

NHMRC Publication- Risk factors associated with SIDS (Oct 1991)

• The possible causes of Sudden Infant Death Syndrome (SIDS), sometimes called cot death, are still not known. However, population studies have identified risk factors that may contribute to SIDS. Risk factors that parents may be able to do something about include; sleeping posture, feeding practices and passive smoking.
• Recent research suggests that babies who sleep on their stomach may have a higher risk of SIDS. The NHMRC recommends that babies should generally sleep on their side or on their back. If on their side, the lower arm should be placed well forward so that babies cannot roll on their stomach. Some babies may need to sleep on their stomach for medical reasons. Parents should discuss with their doctor whether this applies to their baby.
• Breast feeding may reduce the risk of SIDS. Breast milk is the best food for babies. Babies should be breast fed if at all possible.
• Passive smoking is associated with an increased risk of SIDS. NHMRC recommends pregnant mothers should not smoke. This is particularly important during pregnancy and in the baby's first year. Others should not smoke near the baby.
• These risk factors alone do not cause SIDS and it is extremely rare for babies exposed to them to die of SIDS. However, following the above advice may help reduce the number of SIDS deaths. Research is continuing to search for the basic cause of SIDS.
• There has been concern in the community that immunisation is associated with SIDS. There is no scientific evidence to support this belief. No association of immunisation with SIDS has been documented.

References

Reviews | Articles | Search NCBI Bookshelf | Search PubMed

Reviews

• Dwyer T, Ponsonby AL. Sudden infant death syndrome and prone sleeping position. Ann Epidemiol. 2009 Apr;19(4):245-9. PMID: 19344862
• Bacon C. Recurrence of sudden infant death syndrome. Pediatrics. 2008 Oct;122(4):869-70. Review. No abstract available. PMID: 18829813
  

Articles

• Nattie E. Sudden infant death syndrome and serotonin: animal models. Bioessays. 2009 Feb;31(2):130-3. PMID: 19204984
  
• Machaalani R, Say M, Waters KA. Serotoninergic receptor 1A in the sudden infant death syndrome brainstem medulla and associations with clinical risk factors. Acta Neuropathol. 2009 Mar;117(3):257-65. Epub 2008 Dec 4. PMID: 19052756
• Krous HF, Kinney HC. Paterson DS, Trachtenberg FL, Thompson EG, Belliveau RA, Beggs AH, Darnall R, Chadwick AE, Multiple serotonergic brainstem abnormalities in sudden infant death syndrome. JAMA. 2006 Nov 1;296(17):2124-32. PMID: 17077377
  

Search NCBI Bookshelf:

Search PubMed: Search April 2009 "Sudden Infant Death Syndrome" 9006 reference articles of which 1114 were reviews. Search term = Sudden Infant Death Syndrome | SIDS

WWW Links

SIDS Australia On-Line

• Some Answers to your Questions
• Australian Sources of Information and Help

Quitting smoking in pregnancy article 2001 Medical Journal of Australia ABC Health review of this article

ABC Health Articles

• Half of Australian babies are passive smokers - News in Science 14/12/1999
• Vessel blockage linked to infant death - News in Science 18/2/1999
• The effect of maternal smoking on babies - Health Report 23/4/2001

SIDS Links USA

• Medline Plus - Sudden Infant Death Syndrome
• Childrens Hospital & Medical Center (Seattle, WA.)
• Arizona SIDS Alliance
• SIDS Resources of Oregon
• NJ SIDS Resource Center: Homepage
• Babyhood: Health and Safety: SIDS
• Sudden Infant Death Syndrome (SIDS) Network
• The National Maternal and Child Health Clearinghouse has a SIDS page, as well as other useful information.
• Southwest SIDS Research Institute A very informative site from Texas.
• Back to Sleep The National Institute of Health site has quite a bit of information, follow the Back to Sleep link.
• "Compassionate Friends" is a national support organization founded in 1969

Glossary

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

Australian NHMRC Recommendations

The Australian NHMRC (1988) recommends neonates be assessed for follow-up care under the following conditions.

(see the NHMRC WWW Page)

• Birthweight less than 1500g or gestational age less than 32 weeks
• Small-for-gestational-age neonates
• Perinatal asphyxia
• Apgar score less than 3 at 5 minutes
• clinical evidence of neurological dysfunction
• delay in onset of spontaneous respiration for more than 5 minutes and requiring mechanical ventilation
• Clinical evidence of central nervous system abnormalities ie., seizures, hypotonia
• Hyperbilirubinaemia of greater than 350umol/l in full term neonates
• Genetic, dysmorphic or metabolic disorders or a family history of serious genetic disorder
• Perinatal or serious neonatal infection including children of mothers who are HIV positive
• Psychosocial problems eg., infants of drug-addicted or alcoholic mothers.

 

Finally

Each section of the notes covering early development and specific systems contain references to specific abnormalities (on Page 2 of each notes section). The best source for Australian statistical data is the Australian Institute of Health and Welfare National Perinatal Statistics Unit, UNSW which publishes "Congenital Malformations Australia" every 2 years. Be aware that some congenital abnormalities, by their nature, affect multiple systems. In the USA, the Center for Disease Control (CDC) keeps and publishes relevant statistical information. A very difficult issue in abnormal development are the many different Ethical implications.

This current page is a link to Normal and Abnormal Development and Population Data.

Where to Next?

You should look at normal development. Development Notes

Alternatively, go on to look at Systematic Development of organs and tissues.

Quick Links

Development Notes ----------------- Menstrual Cycle Week 1 Week 2 Week 3 Week 4 Placenta Serial Images Genes/DNA Molecular Dev Abnormal Dev Postnatal Dev Notes Index

System Notes ----------------- Heart/Cardiovascular Respiratory Coelomic cavity Gastrointestinal Tract Head and Neck Neural Neural Crest Eye Ear Nose Endocrine Urogenital Musculoskeletal Integumentary

Finally

For those wanting to see dynamic processes of development (and have a reasonably quick connection) then the Movies pages are good for watching changes occur.

Movies ----------------- Embryo Growth Carnegie Stages Ultrasound Images Stage 13/14 Embryo Stage 22 Embryo Heart Septation Neural Neural Crest Other Embryos Larsen Movies

Other Embryos

The study of human development has relied extensively on studying the process in other model animals. For those wanting to see the process of development in other species then the other embryos pages are a good start.

Other Embryos ----------------- Chicken Fly Frog Mouse Rabbit Rat Worm Zebrafish Guinea Pig

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