Context.—The practice of infants cosleeping with adults has long been the subject of controversy. Autopsy findings in cases of sudden infant death syndrome (SIDS) are usually indistinguishable from those found with unintentional or intentional suffocation, and the determination of the cause of death in cases of sudden unexpected death in infancy is often based on investigative findings and the exclusion of natural or traumatic causes.
Objective.—To further elucidate the risk of cosleeping.
Methods.—We reviewed 58 cases of sudden unexpected infant deaths. Cases were excluded if there was any significant medical history or evidence of trauma or abuse.
Results.—Twenty-seven of the infants were cosleeping. Eleven of these cases had been previously diagnosed as SIDS, and in 7 cases parental intoxication was documented.
Conclusion.—Our findings support recent studies that suggest that cosleeping or placing an infant in an adult bed is a potentially dangerous practice. The frequency of cosleeping among cases diagnosed as SIDS in our study suggests that some of these deaths may actually be caused by mechanical asphyxia due to unintentional suffocation by the cosleeping adult and/or compressible bedding materials.
Unintentional or intentional smothering or suffocation of an infant frequently cannot be proven by postmortem examination alone. Physical injuries are usually nonexistent. The diagnosis of the smothering of an infant usually rests on police investigation and/or confession, although cases have been reported in which a parent has falsely confessed to smothering a child, presumably from guilt over the loss of the child.
The diagnosis of sudden infant death syndrome (SIDS) can also be a difficult task for the forensic pathologist. The definition of SIDS, adopted in 1989 by the National Institute of Child Health and Human Development, is “the sudden death of an infant under one year of age which remains unexplained after thorough case investigation, including performance of a complete autopsy, examination of the death scene, and review of the clinical history.”1 The difficulty in the diagnosis of SIDS lies in the fact that the postmortem findings of an infant who succumbs to SIDS are indistinguishable from those of an infant unintentionally or intentionally suffocated or smothered.2
When an infant sleeping with an adult or adults is found dead, the cause of death can frequently not be determined by autopsy findings alone. The results of the autopsies are usually completely negative.3 The potential hazard of an infant cosleeping with an adult has been recognized since Biblical times.4 In 1944, Abramson5 stated that unintentional smothering is “the leading cause of accidental death in early infancy.” More recent authors have also cautioned against the practice of cosleeping,6,7 although others have postulated that the sleeping of infants with their mothers may actually reduce the risk of sudden unexpected death and potentiate the bonding process and breast feeding.8,9
The US Consumer Products Safety Commission10 performed a retrospective review of data collected by their agency of children younger than 2 years who died unexpectedly. The authors concluded that placing a child of this age in an adult bed puts the child at risk of overlay (unintentional suffocation by an adult) or suffocation in bed structures or bedding (wedging). We undertook the current study to further elucidate the potential risk of cosleeping and the relationship of cosleeping to sudden unexpected death in infancy.
MATERIALS AND METHODS
A retrospective review was performed on the autopsy files of one of us (B.C.W.), between 1991 and 2000, for cases of sudden unexpected deaths of infants younger than 1 year. These files consisted of reports of postmortem examinations performed for Upstate New York county coroners' offices. The cases included deaths in which the cause was listed as SIDS, “sudden unexpected death in infancy,” and “undetermined.” Cases were excluded if there was any significant medical history that could have contributed to the infants' deaths or any postmortem or investigative findings suggestive of trauma or abuse.
The reports of the postmortem examinations, including bacteriologic and toxicologic studies, were reviewed, and the microscopic slides, autopsy x-ray films, and photographs were studied. The police investigative files and the birth and medical records of the infants were available for review in all cases, and demographic information was obtained. Data collected included race, age, sex, medical history, and the cause and the manner of death. Investigative information was obtained as to the circumstances of the infants' deaths, including where a child was sleeping and whether the child was sleeping alone or with another individual. In most cases, information pertaining to the sleeping position of the infant was not available. Parental alcohol consumption was noted if this information was provided in the investigative files. Information about parental cigarette smoking was not available.
Fifty-six cases of sudden unexpected deaths of infants younger than 1 year were identified, excluding cases where death was due to an identifiable natural disease or to unintentional or inflicted trauma. These included 43 cases diagnosed as SIDS, in 10 of which the cause of death was listed as “sudden unexpected death in infancy” and the manner of death “undetermined” and in 3 of which both cause and manner of death were best listed as “undetermined.” The cases included 39 male infants and 17 female infants. Thirty-nine infants were white, 1 Hispanic, and 16 African American. Ages ranged from 9 days to 9 months (mean, 2.8 months).
Twenty-three of the infants in our study were found unresponsive in their cribs, whereas 19 were in adult beds and 12 on couches. There was a single case of an infant sleeping in a dresser drawer and one of an infant in a car seat on the floor.
Twenty-nine (51.8%) of the 56 infants were sleeping alone, whereas 27 (48.2%) were cosleeping, including 23 with an adult or adults and 4 with a twin (Table). Fourteen of the cosleeping infants were in an adult bed with an adult or adults, whereas 9 were sleeping with an adult on a couch. In 7 of the 23 cases of infants cosleeping with adults, the adult was documented to be intoxicated. The 4 twin infants were all in cribs. In 8 of the 14 cases of infants cosleeping in adults beds, the diagnosis originally rendered was SIDS. Three of the 9 infants cosleeping with adults on couches had been classified as SIDS deaths, as were the 3 infants sleeping alone on a sofa. No pathologic differences were found at postmortem examination between the cosleeping infants and those sleeping alone.
Of the 29 infants sleeping alone, 19 were in cribs, 5 in adult beds, and 3 on couches. One of the remaining infants was in a car seat and 1 in a dresser drawer on the floor. The deaths of those infants sleeping alone in adult beds were diagnosed as SIDS.
Seventeen autopsy reports documented the presence of central (circumoral) cyanosis. These included 9 infants who were cosleeping and 8 who were sleeping alone. The presence or absence of cyanosis was not noted in the remaining cases.
SIDS claims the lives of many infants every year in the United States. It is the leading cause of death of infants younger than 1 year, with most deaths occurring between 2 and 4 months of age and in the winter. The origin of SIDS remains unclear, despite extensive research. Early theories of thymic enlargement, anaphylaxis to milk proteins, structural abnormalities of the larynx, and viral infections have been discarded.2,11 There is no evidence for genetic transmission.2 Modern research has focused on arousal deficiency and underdeveloped central nervous system cardiorespiratory controls.12
SIDS is a diagnosis of exclusion that can be made only after a complete postmortem examination and investigation of the scene and circumstances of an infant's death. Valdes-Dapena2 estimates that in 85% of cases of sudden and unexpected infant deaths, given a negative history and unremarkable external appearance, no adequate cause of death is apparent. A number of risk factors have been identified, including infant immaturity and low birth weight for the gestational age and maternal cigarette smoking, poor prenatal care, low weight gain, and histories of illicit drug use or sexually transmitted disease.13
Epidemiologic studies have recognized an increased incidence of SIDS among infants sleeping in the prone position.14–16 The American Academy of Pediatrics17 has recommended that healthy infants be placed to sleep on their sides or their backs. The “Back to Sleep” campaign, which focused on alerting parents to the risks of infants sleeping in the prone position, has been followed by a decrease in the incidence of SIDS.15,18
The autopsy findings in cases of SIDS are variable and nonspecific. Petechiae are frequently present on the thymus and pleural and epicardial surfaces, but these petechiae are not necessary for the diagnosis of SIDS, nor does their absence preclude the diagnosis.2 The importance of the finding of cyanosis is controversial. Cyanosis has long been recognized as a sign of asphyxia, and it has been suggested that cyanosis is usually absent in cases of SIDS and that the presence of cyanosis points toward unintentional or intentional suffocation. However, Valdes-Dapena2 reports that cyanosis is often apparent in infants who succumb to SIDS. In the limited number of our cases in which cyanosis was mentioned, there was an approximately equal incidence among infants cosleeping and those sleeping alone, suggesting that the finding of cyanosis cannot be used to rule in or rule out a diagnosis of SIDS.
The potential risk inherent in the practice of the cosleeping of an infant with an adult or adults has been a subject of controversy. Some studies19–25 have reported an increased risk of sudden deaths of infants. Blair and colleagues6 reported a 10-fold increase in the risk of SIDS among infants sleeping in parental beds and a 50-fold increased risk among infants sleeping with a parent on a couch. Increased risk was also associated with recent parental consumption of alcohol. These authors found no increased risk of sudden death among infants who fell asleep in an adult bed but were then put back in their own bed. However, the risk of sudden death of infants sleeping in adult beds was strongly influenced by cigarette smoking and was not significantly increased if the parents did not smoke. Klonoff-Cohen and Edelstein7 found that the risk of SIDS was slightly increased among infants who slept with others, but that the increase was not statistically significant. The risk of death during cosleeping with parents who have consumed alcohol has been stressed.15 In contrast, others have suggested that bed sharing facilitates breast feeding, which might reduce infant vulnerability to SIDS.8 Additionally, Mosko and colleagues9 suggested that a reduced risk of SIDS may be associated with infants sleeping with their mothers, since they reported increased numbers of awakenings during the night. However, laboratory studies of infant arousal do not accurately recreate the situation of an infant unable to breathe because of compression of the face or chest by bed structures or by an overlaying adult who may be intoxicated.
Nakamura and coworkers10 reported the results of a retrospective review of data collected by the US Consumer Product Safety Commission, which found 515 deaths of children younger than 2 years who had been placed to sleep in adult beds. Of these deaths, 121 were attributed to overlay, the unintentional suffocation of the infant by an adult, and 394 deaths were attributed to entrapment in bed structures. The authors then emphasized the hazards of placing a child to sleep in an adult bed.
It has been postulated that the rebreathing of carbon dioxide may contribute to sudden infant death.26,27 This hypothesis has been examined as an explanation for the increased incidence of SIDS among infants sleeping in the prone position.28 The type of infant bedding, particularly soft, compressible materials, may also contribute to the rebreathing of carbon dioxide.26,29,30 The rebreathing of carbon dioxide should therefore be considered as a factor in the sudden infant death of cosleeping infants.
Forty-eight percent of the infants in our study who died unexpectedly and had no distinct autopsy findings were cosleeping. Most of these cases had been diagnosed as SIDS, but the high incidence of cosleeping suggests that external factors may have contributed to some of these deaths. These findings support recent studies that suggest that cosleeping or placing an infant in an adult bed is a potentially dangerous practice. Possible factors that contribute to the deaths of cosleeping infants include unintentional suffocation due to overlay by an adult and/or entrapment in bed structures. The rebreathing of carbon dioxide associated with compressible bedding may also play a role. Because information pertaining to potential cigarette smoking was not available in our cases, further study is needed to clarify the role of cigarette smoking and the sudden unexpected death of cosleeping infants. Additionally, because of the decreased incidence of SIDS among infants sleeping on their backs, it would be valuable to study the sleeping positions of cosleeping infants who die suddenly.
Presented in part at the 2001 meeting of the American Academy of Forensic Sciences, Seattle, Wash, February 22, 2001.
Reprints: Barbara C. Wolf, MD, 6065 Ellis Lane, Loxahatchee, FL 33470