SIDS, or Sudden Infant Death Syndrome, is every new parent’s worst nightmare. There are few sadder things to contemplate than the new, healthy life you are nurturing leaving the world unexpectedly and so soon. And because science hasn’t been able to completely explain SIDS yet, it becomes more terrifying for us.

But we do know some things about SIDS. New data and research, while not conclusive, make a strong case against certain risk factors, and can give parents a better idea of what to do, what not to do, and how much to worry.

What is Sudden Infant Death Syndrome?

Sudden Infant Death Syndrome describes a situation when a healthy infant under 1 year of age dies suddenly and unexpectedly, and with no apparent cause upon investigation. The accepted theory is that babies who die of sudden infant death syndrome are unable to rouse themselves from sleep and cry when oxygen is in short supply, as would typical babies.

How likely is SIDS?

Unfortunately, no one knows how common sudden infant death syndrome is in India.

“Our reporting system of infant deaths is not accurate, which makes it hard to record a SIDS case,” says Dr. Tushar Maniar, head of pediatrics and neonatology at Nanavati Super Speciality Hospital in Mumbai.

The best we can do is look at Western data. In the US, roughly 0.55 babies for every 1,000 died of sudden infant death syndrome in 2006, a figure that has more or less held steady in the intervening years. (The figure also may also be slightly inflated, as SIDS is often recorded even when there’s a clear cause of death, out of concern for parents’ feelings.)

This is after a 20-year awareness campaign, which is credited with halving the rate of SIDS deaths, so it is possible that in India, where no such campaign exists, the prevalence could be higher.

However, it’s equally possible the figure could be lower; a 2011 study in the UK found a lower rate of sudden infant deaths among Indian, Pakistani and Bangladeshi families than in White British families, likely because SIDS-preventative sleeping practices and infant care were more culturally endemic among South Asians.

Regardless, SIDS is a rare occurrence anywhere.

What do we know about SIDS risk factors?

Risk factors are, by definition, possibilities. There is no guarantee that an infant who experiences one of the following will die of SIDS, nor that the reverse means he or she won’t. However, the following behaviours and actions have been linked to most cases of sudden infant death syndrome – typically in combination.

Underlying problem

This is the unknown, x-factor of SIDS. Experts agree that most babies who die suddenly and inexplicably have a predisposition that puts them at great risk when exacerbated by other risk factors, but science has been unable to find what that underlying condition is.

Whatever it is, it does not appear to be linked to gender. While research has indicated boys are more likely than girls to die of SIDS, subsequent studies have found it is not due to an inherent difference in gender. If anything, research has found male infants to be more likely than female infants to rouse themselves in the first few weeks of life, leading experts to posit the uneven gender divide could be due to parents trying to calm restless boy babies by changing their sleeping position to a more risky one (see below).

Developmental stage

One of the most recent and interesting insights into SIDS deaths in recent years is the finding that most occur during critical developmental growth spurts, particularly between the ages of six weeks to three months.

Delayed development has been associated with SIDS; premies and babies with low birth weight are more at-risk. And babies exposed to tobacco smoke – whether in utero, or after birth – can have developmental difficulties that put them more at-risk for SIDS. Maternal use of drugs or alcohol is also thought to confer increased risk.

External stress to breathing / temperature

This is the best understood risk factor for SIDS, and most prevention campaigns revolve around limiting potential stressors to the sleeping baby. The stressor with the most evidence is the baby’s sleeping position – babies put to sleep on their stomach or side are at higher risk of SIDS.

Similarly, sleeping environment is also an accepted external risk factor; babies who sleep on fluffy mattresses or with loose and fluffy bedding or stuffed toys are at an increased risk of SIDS, as are babies who sleep in the same bed as their parents, who may unconsciously roll on top of them.

Less confirmed external stressors include swaddling after six months. Researchers – in a study they admit had limitations – found a link between SIDS and infants who were swaddled during sleep after six months of age.

The theory is that at this age, babies have developed the ability to roll over, but, because of the swaddle, are unable to roll again onto their backs, thus putting them at risk of SIDS. For this reason, researchers recommend babies older than two months not be swaddled.

Covering a baby with a cloth – as in covering a pram to guard against sunlight — could also stress breathing and temperature.

What do we know about SIDS prevention?

While there is sadly no infallible prescription for preventing SIDS, enough evidence has been gathered to suggest the following actions and behaviours diminish the external stress risk.

Sleeping on back

This is by far the most proven way of lowering SIDS risk. The 20-year campaign to reduce unexplained infant deaths in the US revolved around putting babies to sleep on their back instead of their side or stomach. That same time span saw the number of annual SIDS deaths reduce by half. (Note that it’s fine if the child moves him or herself into a side or stomach position during sleep; guidelines do not suggest resettling a child on his or her back mid-sleep.)

Sharing a room

Experts say sharing a room for the first 6 to 12 months lowers the risk of SIDS. However, they note, this does not mean sharing a bed. Parents are advised to let the infant sleep in a bassinet or crib near the parents’ bed.

Breastfeeding

Infants who are breastfed are less likely to die of SIDS; the link is clear, even if it’s not established that breastmilk itself is responsible for preventing SIDS deaths. There is some thought that a strong immune system – which breastmilk undoubtedly contributes to – reduces exposure to the respiratory and gastrointestinal infections that could put infants at risk for SIDS; other theories hold that breastfed infants awaken more easily at night.

Using a pacifier

Studies have also found a link between pacifier use and reduced risk of sudden infant death syndrome, though it is unclear precisely what that link is.

What do we know about the actual cause?

The key to SIDS is cracking the underlying defect, the x-factor. Unfortunately, we don’t have any facts right now, only theories being tested. Here are some of the more promising areas scientists are exploring.

Low serotonin levels in the brain

Researchers have found many babies who died of SIDS had unusually low levels of the neurotransmitter serotonin, which can affect breathing, heart rate, body temperature and the ability to rouse from sleep (among others). When SIDS was simulated in rats, serotonin injections into the brain stem proved helpful. However, it’s important to note this finding, though important and hopeful, is far from applicable to human babies.

Abnormal hippocampus

Related research has found abnormalities in the hippocampus – an area of the brain that influences breathing, heart rate, and body temperature – in 40% of a group of babies who died of SIDS. (The abnormality was also found in a group of infants who died of explained causes, though in much smaller numbers.)

Inner ear damage

Studies have also pointed to inner damage as a common thread in SIDS deaths. Damage to the inner ear, researchers posit, could inhibit babies’ ability to wake up and re-position themselves to get more oxygen. Research is currently underway.