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  • Sudden Infant Death Syndrome (SIDS)

    Sudden infant death syndrome (SIDS) has been reported to be the leading cause of infant death beyond the newborn period. Cited to be the commonest cause of death between 28 days and 12 months, SIDS accounts for two fifths of all postnatal deaths, the cause or the causes still elude us demanding a continuing research!

    What is Sudden Infant Death Syndrome (SIDS)

    Sudden infant death syndrome has been defined as “the sudden death of an infant under one year of age, which remains unexplained after a thorough case investigation, including performance of a complete autopsy, examination of the death scene and review of the clinical history.” It occurs less frequently in the first month of life, the risk is highest between 2 and 4 months of age, decreasing thereafter. The boys are more affected as compared with the baby girls.. Almost 90% of the reported cases took place in the first six months of life.

    Etiology of SIDS

    Anecdotal evidence suggests that some of the infant deaths are due to upper airway obstruction. Obstructive apnoea has been suggested as a possible reason for SIDS. Another group of investigators have shown that the hypoxanthine concentration was found to be raised in the vitreous humor of babies dying from SIDS. Hypoxanthine is a breakdown product of adenosine monophosphate, a catabolic process accelerated by hypoxia, providing supportive evidence that babies suffered from recurring hypoxia before death.

    It has also been suggested that many infants die due to a viral upper respiratory tract infection, which may have led to hyperpyrexia and central apnoea causing SIDS. Another study claims that babies dying due to SIDS may have a defect of immune system. An increased concentration of IgG, IgM and may be IgA was reported in the lungs of these babies.

    Autonomic impairment or immature cardiorespiratory autonomic control, and a failure of arousal responsiveness from sleep are also known to cause SIDS.
    Increasingly developing research has shown that SIDS may be the consequence of a primary underlying genetic disorder, including inborn errors of metabolism (Especially fatty acid metabolism disorders), genetic defects of cardiac conduction and hypertrophic cardiomyopathies.

    Risk factors for SIDS

    A triple risk model has been suggested for SIDS risk;

    · A vulnerable infant
    · A critical developmental period in homeostatic control
    · Exogenous stressor, such as being placed for sleep in the prone position

    The generally recognized risk factors for SIDS as reported in research studies are;

    Maternal smoking and smoke exposure

    Maternal smoking during pregnancy and postnatal exposure to tobacco has emerged as separate risk factor for SIDS. Prenatal smoke exposure causes decreased lung volume and compliance, decreased heart rate variability to stress; nicotine has neuroteratogenic effects resulting in decreased arousal to hypoxia and other stimuli.

    Sleep practice and environment

    The side sleep position has increased the risk to SIDS. Side sleep position is unstable and infants may roll to prone increasing the risk of SIDS. Soft bedding and soft surfaces including pillows, quilts, comforters, sheepskin and porous mattresses are all important risk factors. Warmer room temperature and multiple layers of clothing or blankets on the infant also act as a risk factor. Bed sharing with smoking mothers or after consuming alcohol may prove hazardous for the baby.

    Infant medical condition

    Premature infants or those with low birth weight are at an increased risk of SIDS. Apnoea, upper respiratory tract infection are other risk factors for SIDS.


    Siblings of SIDS victims are at an increased risk. This may be due to genetic or metabolic disorders.

    Prevention of SIDS

    The risk to SIDS may be reduced to cut down the deaths of the infants. American Academy of Pediatrics has recommended some suggestions for reducing the risk factors for SIDS.

    · Back to sleep, infants should be kept in supine position. Side sleeping is not considered safe.
    · Use a firm sleep surface.
    · Do not use soft toys or loose objects for infants.
    · DO not smoke during pregnancy and after delivery.
    · Co sleeping is not recommended. A separate but proximate sleeping environment such as a cot or bassinet close to parent’s bed is preferred.
    · Breastfeeding is considered protective for SIDS risk.
    · Do not overheat
    · Offer a pacifier to the baby at nap time and bed time. Do not reinsert it once the baby goes to sleep.
    · Avoid development of positional plagiocephaly, encourage “tummy time” when the infant is awake and playful.
    · Do not excessively use car seats or bouncers.

    Despite a definite reduction in the cases of SIDS, there still needs a lot to be done in the field. A definitive search strategy is required to look into the causes, pathophysiology of SIDS and suggest effective interventions to avoid the risk of SIDS.

    Image courtesy: " Tomorrow's Child, Michigan SIDS"'s Child, Michigan SIDS"


    Christodoulou, J. (2013, February). Advances in the Genetic Investigation of Sids. Pathology, 45.
    Milner, A. (1989, March 18). Sudden Infant Death Syndrome Recent focus on the respiratory system. British Medical Journal, 298, 689-690.
    Moon, R. Y., Horne, R. H., & Hauck, F. R. (2007, November 3). Sudden Infant Death Syndrome. The Lancet, 370, 1578-1587.
    Comments 2 Comments
    1. Widaa's Avatar
      Widaa -
      Great article Pooja and very interesting. I'm sure this will benefit many people with in regards to sudden infant death, allowing them to understand the risk factors and ways by which one can work to prevent such an outcome in their newborn.
    1. Unregistered's Avatar
      Unregistered -
      My name is Armando. My wife recently had our first baby. She breastfed baby for the first six days. on the 6th day our dr told us it was okay to pump and bottle feed. Baby did fine all day in her rocker (where she was slightly sitting up). We quickly noticed that baby ate more from the bottle, also that baby slept more soundly throughout the day. We thought great! So before bedtime, we fed baby from the bottle, burped her like normal, and laid her down flat in her crib about 45 minutes after she was burped. Definitely long enough to let her food settle. Being she is our first baby, I was up for every movement baby made, didn't bother her or anything, just let her sleep as she got comfortable. about 20 minutes in, I noticed her breathing was starting to sound like she had fluid in her throat. not a lot, she was still breathing, but it got worse pretty quick. within about five minutes I had her in my hands slapping her back getting the fluid out. she started breathing again after that, but it took her a few minutes to recover, then she was finally able to let out a cry.

      All studies say that babies that are breastfed are less likely to die from SIDS. All studies say that suffocation seems to be common in autopsies. over HALF of baby deaths are a result of SIDS.

      Now my questions and concerns start. I am sure there is a perfectly good reason drs have told the world to lay baby flat on her back for bed time. but, have you ever ate something or especially drank something and laid on your back, straight on your back? it comes back up! No matter what age. Imagine if you had a full enough stomach to put you to sleep.

      Mommies do not send out an incredible amount of milk when breastfed, it is no wonder to me why babies that are breastfed are more likely to stay alive. they dont have enough in their tummy to be full. everything that I have read on the studies seem to point to babies choking up their food. and that night was validation enough. maybe people do not find it in the autopsy because by the time baby is in the autopsy, everyone has turned the baby in every direction trying to figure out what is wrong, the milk goes back down.

      Baby will sleep in rocker tonight where she will be slightly sitting until we find a solution. maybe tilting her bed down an inch or two so her head is above her feet? that leads to many other problems as you can lead on to. What about not laying her flat on her back not so soon after? well If most babies are under age 1, maybe ever 45 minutes is not enough, as it wasn't for our little girl. Thank God we caught it.

      Maybe someone can study babies whos heads are slightly elevated? If 50% of SIDS cases are related to asphyxiation then choking on recently ingested milk from a bottle is a great place to start. imagine eliminating 50% of SIDS deaths.
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