Share this article on:

Observations on Increased Accidental Asphyxia Deaths in Infancy While Cosleeping in the State of Maryland

Li, Ling MD*§; Zhang, Yang†; Zielke, Ron H. PhD‡; Ping, Yan MD§; Fowler, David R. MD*‡

American Journal of Forensic Medicine & Pathology: December 2009 - Volume 30 - Issue 4 - pp 318-321
doi: 10.1097/PAF.0b013e31819df760
Original Article

The Office of the Chief Medical Examiner (OCME) has recorded a significant increase of accidental asphyxia deaths in infancy associated with cosleeping in the state of Maryland in 2003. A total of 102 infants died suddenly and unexpectedly during 2003 in the state of Maryland. Of the 102 infants, 46 (45%) were found cosleeping. The frequency of cosleeping among these 102 infants was 28% (29/102) for black infants and 15% (15/102) for white infants. Ten of the 46 cosleeping infant deaths (20%) were determined to be the result of accidental asphyxia, and 28 cosleeping infant deaths (59%) were classified as “undetermined” because the possibility of asphyxia due to overlay while cosleeping could not be ruled out. Only 21 cases were determined to be Sudden Infant Death Syndrome (SIDS), which is consistent with the continuous decline of SIDS death in Maryland since 1994. The age of asphyxiated cosleeping infants ranged from 15 days to 9 months. Nine out of the 10 asphyxia deaths were black infants. The most common sleeping location of the asphyxia infants was on a couch/sofa, followed by an adult bed.

Crib availability was documented in all of the cosleeping cases. A majority (61%) of the cosleeping infants (28/46) had an available crib or bassinet at home and 9 out of 10 asphyxiated cosleeping infants had a crib at home at the time of the incident.

This report focuses on the detailed scene investigation findings of infant victims who died of asphyxia while cosleeping. The shift of diagnosis in sudden infant death investigation is also addressed.

From the *Key Laboratory of Evidence Science (L.L., D.R.F.), China University of Political Science and Law, Beijing, China, and the Office of the Chief Medical Examiner (L.L., D.R.F.), State of Maryland, Baltimore, Md; †College of Chemical and Life Sciences (Y.Z.), University of Maryland, College Park, Md; ‡Department of Pediatrics (L.L., R.H.Z., D.R.F.), University of Maryland School of Medicine, Baltimore, Md; and §the Department of Forensic Medicine, (L.L., Y.P.), Wuhan University, China.

Manuscript received January 11, 2007; accepted February 14, 2007.

Supported, in part by the Center for Infant and Child Loss in Maryland and the NICHD Brain Tissue Bank for Developmental Disorders, University of Maryland, School of Medicine.

The authors would like to thank Dawn Zulauf and Sheldon Lapan for their computer technical support and Eleanor Thomas for her clerical support.

Reprints: Ling Li, MD, Office of the Chief Medical Examiner, State of Maryland, 111 Penn Street, Baltimore, MD 21201. E-mail:

During the past decade, considerable attention has been focused on the difficulties that exist in distinguishing between the unintentional or intentional suffocation (asphyxiation) of an infant and Sudden Infant Death Syndrome (SIDS).1–3 When an infant is found dead in a cosleeping situation (sharing a sleep surface with another person or persons), autopsy examination alone can result in failure to identify accidental mechanisms in cosleeping infant deaths because physical evidence of asphyxia is usually nonexistent.2,4–5 The diagnosis of asphyxia death versus SIDS is a challenging task for the forensic pathologists.

To reach a proper conclusion as to the cause and manner of death of an infant who died suddenly and unexpectedly, a complete postmortem investigation including review of clinical history, death scene investigation as well as autopsy examination must be thorough and professional. We undertook this study to highlight the importance of infant death scene investigation and to further elucidate the potential risk of cosleeping for sudden unexpected infant deaths, especially by accidental asphyxia. The shift of diagnosis in sudden unexpected infant deaths is also discussed.

Back to Top | Article Outline


The Office of the Chief Medical Examiner (OCME) is responsible for investigation of all sudden and unexpected deaths in the state of Maryland. In 2003, a total of 102 infants (≤1 year of age) who died suddenly and unexpectedly in Maryland were investigated and autopsied by the OCME. A retrospective review was performed on the autopsy files of all 102 cases. The files consisted of police and medical examiner investigator's reports and reports of postmortem examinations. Data collected included race, sex, age, medical history, autopsy findings, and the cause and manner of death. Investigative information was obtained as to the circumstances of the infants' deaths, including sleeping location and whether the infant was sleeping alone or with another person or persons. The crib availability was documented in all cosleeping infants. Parental alcohol and drug use was noted if this information was provided in the investigative reports.

Back to Top | Article Outline


The cause and manner of death of infants in the study are showed in Table 1. Of the 102 cases, 44 (43%) infant deaths were due to natural causes, including 21 (20%) SIDS cases. Fifteen (15%) deaths were the result of accident and 7 (6%) were homicide. The manner of death could not be determined in more than one third (35/102) of the infants, in which the cause of death was listed as Sudden Unexplained Death in Infancy (SUDI). One infant died of near drowning with an undetermined manner.

For all cases, sleeping location was recorded. Only 24 (24%) infants were found sleeping alone in a crib or bassinet. Infants were found on a sleep surface not designed for infants in 76% of the cases. The data showed that 45% (46/102) infants were cosleeping (in bed with another person or persons) at the time when they were found unresponsive. Comparison of sleeping location in SIDS, accidental asphyxia, and SUDI infants is seen in Table 2. Of the 21 SIDS infants, 11 (52%) were found unresponsive in a crib/bassinet alone, 3 were sleeping alone in an adult bed, whereas 4 were cosleeping in an adult bed. There was one SIDS infant sleeping alone in a couch, one in a baby swing, and one in mother's arm. Ten out of the 11 asphyxia infants and 28 of 35 (80%) SUDI/undetermined infants were found sharing a sleep surface with someone else (cosleeping).

We have seen a sharp increase of accidental asphyxia death in cosleeping infants in Maryland in 2003 (Fig. 1). Before 2003, the number of diagnosed accidental asphyxia deaths in cosleeping infants ranged from 0 to 4 cases with an average of 2 cases a year in Maryland. However, in 2003, ten deaths were attributed to accidental asphyxia while cosleeping. There was a single case of an infant who was found wedged between the mattress and wall near a space heater after being placed sleeping in an adult bed alone. In 28 infants, their cause of death was certified as SUDI and manner of death was “undetermined” because the possibility of asphyxia due to overlay while cosleeping could not be ruled out.

The age, race and sex distribution of the asphyxiated cosleeping infants is seen in Table 3. The ages ranged from 15 days to 9 months with 7 infants being less than 3 months of age. Nine out of ten (90%) were black infants. Four infants were premature at birth. The scene investigation and autopsy findings were analyzed (Table 4). Of the 10 cases designated as accidental asphyxia, 5 infants were found cosleeping in a couch/sofa (50%), 4 infants (40%) in a regular adult bed, and one in a recline chair. The victims were cosleeping with the mother in 4 cases, the mother and older sibling in 2 cases, the father 2 cases, the older sibling in 1 case, and a 14-year-old babysitter in 1 case. The ages of cosleepers ranged from 3 years to 24 years with 6 of them less than 20 years of age. Four victims were found unresponsive underneath the cosleeper, one infant's face covered by the cosleeper's arm, 2 victims wedged between the back of couch and the cosleeper, one wedged between mattress and wall, one wedged between headboard and wall, and one face down on a pillow next to the cosleeper. In 9 out of the ten cases, the cause of death was determined mainly based on death scene investigation (the events were witnessed by a third party) with complete negative history and autopsy finding; 4 cases were classified as asphyxia due to overlay, 4 as positional/compressional asphyxia, and one as asphyxia. There was a single case of an infant sleeping in a couch next to the mother who was overweight. When the mother woke up, she found the infant face down in a pillow next to her. Postmortem examination revealed that there were petechial hemorrhages of both conjunctivae, with no other injuries or any natural disease noted. The mother admitted that she had consumed alcohol before she fell asleep next to the infant on the couch. Therefore, the infant death was classified as asphyxia due to overlay (Table 4, case 2).

The characteristics of cosleeping infants and crib availability were also documented. Of the 102 infants, 46 (45%) were found cosleeping. Fifteen cosleeping infants were white and 29 were black (Table 5). A majority (28/46) of cosleeping infants had a crib or bassinet available at home (Table 6). Nine out of the 10 asphyxiated cosleeping infants had an available crib or bassinet at home at time of the incident.

Back to Top | Article Outline


Many investigations have been undertaken looking at aspects of infant sleeping environments that may be linked to the risk of sudden death in infancy. Prone sleeping, maternal cigarette smoking, cosleeping and overheating are considered significant potentially modifiable risk factors for SIDS.6–8 Of further considerable interest as well are features of infant sleeping arrangements that may cause death from asphyxiation.

Although the incidence of SIDS has declined substantially as a result of the back to sleep campaign in the United States and elsewhere, the proportion of sudden, unexpected deaths diagnosed as accidental suffocation/asphyxiation and related preventable causes may be increasing.9,10 A recent study11 analyzing all accidental suffocation deaths among infants reported to the US Consumer Product Safety Commission found increasing trends in the 1990s for reported deaths of infants who suffocated on sleep surfaces other than those designed for infants. During the same time period, there has been a substantial decline for suffocation deaths in cribs.

Our study shows that number of infant deaths diagnosed as accidental asphyxia, particular involving in infants who were cosleeping on couches/sofas and in adult beds, increased dramatically in Maryland, 2003 (Fig. 1). Of 11 infants who died of asphyxia in this study, 10 were found cosleeping either on a couch/sofa (N = 5), or an adult bed (N = 4), or a recline chair (N = 1). One infant was sleeping in an adult bed alone. None of the deaths occurred in cribs. Since the publication of federal regulations12 regarding construction of cribs and many reports of accidental deaths due to defective or poorly designed infant cribs/ cradles,4,13,14 the number of suffocation deaths in cribs in the United States has decreased significantly.11 However, it is only recently that the potential dangers of accidental deaths associated with cosleeping have been emphasized.11,15 It is important to recognize that infants cosleeping on couches/sofas are especially at risk for suffocation either due to overlay or entrapment/wedging between the back of sofa and a cosleeper as was seen for 5 infants in the presented series.

In the experience of the authors or others, autopsy alone is frequently insufficient to differentiate between SIDS and suffocation, or death due to a compromised airway.15,16 Like SIDS victims, asphyxia victims due to overlay and entrapment in infants usually have a complete negative autopsy.17 When the infant was found in bed with another person at the time of death, determination of the cause of death relies on a thorough scene investigation/reconstruction. In our study, the diagnosis of asphyxia due to overlay or entrapment by the cosleeper was made in 9 out of 10 cases by witness report (found by a third party) or report by the overlay person him/herself. Because the risk for the accidental asphyxiation/suffocation due to unsafe sleeping environments can be modified, it is extremely important for the investigators to carefully examine the scene and personally interview the individuals caring for the infant and the first person who discovered the child, and gather data from agencies or persons providing services to the family and child.

The increase in the number of reported suffocation deaths in infancy has been explained by increased reporting system and diagnostic shift, in addition to a real increase.11,18 There has been an upward trend since the late 1990s in the number of scene visited and detailed description of the scenes by the medical examiner's office in Maryland and elsewhere,15,19 likely due to the increased awareness of hazardous infant sleeping environments.

We have also recorded a significant increase of “undetermined cases” in 2003. Our study showed that more than one-third of (36/102) infants were assigned as “undetermined.” It was noted by our previous study15 that as the SIDS rate in Maryland dropped significantly in the past 10 years, the occurrence of related diagnosis, such as “undetermined cases” has increased considerably from 2.1% cases in 1990 to 19.3% in 2000. The further increase of “undetermined” cases was largely due to the concern of the possibility of asphyxia due to overlay while cosleeping as was seen for 28 out of 36 (77%) “undetermined” cases in this study. Since the diagnosis of SIDS must be made by exclusion, it is important to exclude asphyxia due to overlay in cosleeping infants. It is authors' opinion that the increasing trend in the diagnosis of accidental asphyxia and “undetermined” among cosleeping infants in Maryland most likely reflects the fact that the question of possibility of asphyxia due to overlay or entrapment while cosleeping was finally being recognized and emphasized, and that a more thorough death scene investigation led to increased information.

Placing infants to sleep on surfaces shared with another person or persons exposes them to potentially fatal hazards. These hazards include overlay by cosleeper; entrapment/wedging between the bedding and cosleeper or between mattress and wall, head entrapment in bed railings, and suffocation on soft bedding or waterbeds.20 It has been our experience, when talking to the parents or caretakers of these accident victims, the topic of potential risk of suffocation while cosleeping is rarely mentioned. Our investigation showed a majority (61%) of cosleeping infant victims had a crib/bassinet available at home and 9 of the 10 asphyxia cosleeping victims had a crib available at the time of incident. The parents or caretakers usually did not recognize the potential danger of accidental death due to cosleeping.

In conclusion, a more intense public education on these avoidable and modifiable unsafe sleeping environments should be carried out and efforts to get the information about the potentially fatal consequences of cosleeping to the parents and caretakers should be promoted.

Back to Top | Article Outline


1. Beal SM, Byard RW. Accidental death or sudden infant death syndrome? J Paediatr Child Health. 1995;31:269–271.
2. Collins KA. Death by overlaying and wedging, a 15-year retrospective study. Am J Forensic Med Pathol. 2001;22:157–159.
3. Person T, Lavezzi WA, Wolf BC. Cosleeping and sudden unexpected death in infancy. Arch Pathol Lab Med. 2002;126:343–345.
4. Smialek JE, Smialek PZ, Spitz WU. Accidental bed deaths in infants due to unsafe sleeping situations. Clin Pediatr. 1997;16:1031–1036.
5. Byard EW, Beal S, Bourne AJ. Potential dangerous sleeping environments and accidental asphyxia in infancy and early childhood. Arch Dis Child. 1995;71:497–500.
6. Blair PS, Fleming PJ, Smith IJ, et al. Babies sleeping with parents: case-control study of factors influencing the risk of sudden infant death syndrome. BMJ. 1999;319:1457–1462.
7. Mitchell EA, Tuohy PG, Brunt JM, et al. Risk factor for sudden infant death syndrome following the prevention campaign in New Zealand: a prospective study. Pediatrics. 1997;100:835–840.
8. Panaretto KS, Smallwood VE, Cole P, et al. Sudden infant death syndrome risk factors in North Queensland: a survey of infant-care practices in indigenous and non-indigenous women. J Paediatr Child Health. 2002;38:129–134.
9. Centers for Disease Control and Prevention. 1980–1998 infant suffocation deaths and rates. Available at:
10. Drago DA, Dannenberg AL. Infant mechanical suffocation deaths in the United States, 1980–1997. Pediatrics. 1999;103(5): available at:
11. Scheers NJ, Rutherford GW, Kemp JS. Where should infants sleep? A comparison of risk for suffocation of infants sleeping in cribs, adult beds, and other sleeping locations. Pediatrics. 2003;112(4):883–889.
12. Code of Federal Regulations: Title 16-commercial Practice, Part 1508-requirements for Full-size Baby cribs. P. 620-622 Available at:
13. Moore L, Bource A, Beal S, et al. Unexpected infant death in association with suspended rocking cradles. Am J Forensic Med Pathol. 1995;16(2):177–180.
14. Variend S, Usher A. Broken cots and infant fatality. Med Sci Law. 1984;24:111–112.
15. Li L, Fowler D. Lui Li, et al. Investigation of sudden infant deaths in the state of Maryland (1990–2000). Forensic Sci Intl. 2005;148:85–92.
16. Smialek JE, Lambros Z. Investigation of sudden infant death. Pediatrics. 1988;15:191–197.
17. Gilber-Barness E, Hegstrand L, Chandra S, et al. Hazards of mattresses, beds, and bedding in deaths of infants. Am J Forensic Med Pathol. 1991;12:27–32.
18. Mitchell E, Krous HF, Donal T, et al. Changing trends in the diagnosis of sudden infant death. Am J Forensic Med Pathol. 2000;21:311–314.
19. Perrizo K, Pustilnik S. Association between sudden infant death in infancy and co-sleeping: a look at investigation methods for Galveston county medical examiners office from 1978–2002. Am J Forensic Med Pathol. 2006;27:169–172.
20. Nakamura S, Wind M, Danello M. Review of hazards associated with children placed in adult bed. Arch Pediatr Med. 1999;153:1019–1023.

Accidental asphyxia; sudden infant death; cosleeping; scene investigation

© 2009 Lippincott Williams & Wilkins, Inc.