Commonly Asked Questions About SIDS: A Doctor's Response

By J. Bruce Beckwith, MD

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The following information was excerpted from a speech entitled, "Using Accurate Information," presented on January 29, 1983 at a workshop for parent contacts, "Healing Grief: Helping the Survivors of Sudden Infant Death." The information was updated by Dr. Beckwith in January 1996.

Dr. Beckwith is a pediatric pathologist and was a principal member of the SIDS Research Team at Children's Hospital and the University of Washington, Seattle, from 1964 to 1984. He has authored or co-authored numerous research publications on SIDS. He is currently Head of the Division of Pediatric Pathology at Loma Linda University, Loma Linda, CA.

I. What Is The Cause Of SIDS?

It is common for the daily media to gleefully report that "the cause" for SIDS has been discovered. Over the years I have worked with SIDS, literally hundreds of such reports have appeared, and to date not one of them has passed the test of time. One of the most common causes for misunderstanding is the failure to distinguish risk factors from causes. For example, maternal smoking, viral infections, tummy sleeping, or prematurity have all been touted as "causes" for SIDS. Yet, most infants exposed to these risk factors will live, and many SIDS victims will have none of these risk factors.

I think of SIDS, not as a disease, but as a manner of dying. It is the result of an episode that likely occurs very rapidly, perhaps over just seconds or minutes, that results in death of the infant. This episode seems to be something to which the developing human is at risk over a relatively short period of time, perhaps related to critical maturational stages that the infant passes through after the neonatal period, but during the early months of postnatal life.

I have long believed that the answer to SIDS will come, not by looking at predisposing factors, but by working backwards from the moment of death. What exactly is the mechanism of death? Is it due to airway obstruction, cessation of the drive to breathe, stoppage of the heart, or some catastrophic event in the developing brain? By answering the question about exact mechanism of death, we can work backwards more efficiently to causes for that type of event, and from those to predisposing factors.

I spent many years presenting evidence that suggests the mechanism of death may be a sudden internal obstruction of the upper airway, probably at the very end of a breath. The sleeping baby lets out air, and something closes down inside the throat that prevents the intake of the next breath. The infant cannot cry out, but may change position as a result of this event. The baby may get into situations suggesting external suffocation during this episode - the face becomes straight down into the bedding, or wedged into a corner of the crib, or blankets are pulled up over the face. This findings may lead to a false suggestion that the cause of death is external suffocation. But they are not the cause of death, they are the result of the dying episode.

If the autopsy suggests airway obstruction, how can we so confidently rule out external suffocation as the cause for SIDS? One of the most compelling arguments is that the autopsy findings are identical in babies dying of SIDS with the face entirely uncovered to those where the face is covered.

The main evidence for airway obstruction is the presence of tiny hemorrhages, called petechiae, which are present over the surfaces of the organs inside the chest cavity, but not elsewhere, in the great majority of SIDS victims. Such petechiae are present in nearly 90 percent of SIDS victims. They are far less common in infants or children dying of external suffocation. Our research indicates a potential reason for the hemorrhages seem to be the result of suction pressures inside the chest that can only

In conclusion, I do not know the cause of SIDS, though I believe the mechanism may be a sudden internal obstruction of the upper airway during sleep. There may never be a single "cause" that can be identified.

II. Why Can A Healthy Baby Die So Suddenly

Why would the airway become obstructed during sleep in a healthy and thriving baby? Nobody knows for sure. If one accepts that we understand how they die, the next question is why do they die? A concept that I have found appealing for many years is that this stoppage, or obstruction, of the airway is not due to a disease process or abnormality of the baby, but is a reflection of the fact that babies at this time of life are undergoing an incredibly rapid state of growth and maturation.

Many important changes are occurring at the age when most SIDS occur. The infant is, among other things, coming into an age where he is beginning to sleep through the night. That's not just a simple change in habit pattern, but a change that is very fundamental and has to do with control mechanisms in the brain. Centers that are beginning to be active in the baby's brain didn't even exist when that infant was born. Virtually all of brain growth occurs in the first two years of life and the growth rate in the first six months is the most rapid of any time in life. During the time when these important control centers are in a period of transition, abnormal messages might come down to the organs of respiration, one of which is to "close off" rather than "open up." Normally, at the end of a breath, the throat collapses or closes, then opens up prior to a new breath being taken. But, if the wrong message comes down from the brain, the throat may stay closed instead of opening. That wrong message isn't necessarily a result of this baby being abnormal, but occurs in a normal baby whose brain is growing at a tremendously rapid pace.

This view of SIDS is certainly one person's view, it's not shared by everybody who works in SIDS. It's a view which I find very reasonable and helpful; the concept is that the baby was normal when it dies, not abnormal. There is no way for anyone to predict that a normal baby is going to have this kind of abnormal event. Many factors may contribute to that event. Minor irritation of the airway may, by increasing the sensory input coming up the nerves from the throat to the brain, increase the likelihood of abnormal messages to come down. Thus, perhaps we have a connection with the minor respiratory infections which are present in many cases.