Repeat sudden unexpected and unexplained infant deaths: Natural or unnatural?

Some assume that, when there are 2 or 3 unexpected and unexplained infant deaths in a family, they are likelier to be unnatural than natural. The chance of a second infant death being natural or unnatural was examined inthe context of the Care of Next Infant (CONI) program in the United Kingdom, which supports parents who previously had an unexplained infant death. The study group included 6373 infants from 5229 families who completed the CONI program. Approximately one fifth of infants were siblings of an earlier CONI infant. The previous death and the CONI death were assessed by a family interview, an autopsy review, and a case discussion. The 57 CONI infants who died within the first year of life represent an incidence of 8.9 per 1000. Nine of these deaths were inevitable, whereas 48 were unexpected. Two families lost 2 children each. Forty of the 46 first CONI deaths were natural. Six were classified as probably homicides, 5 of which were committed by 1 or both parents. Two families probably had covert double homicides. The odds ratio that 2 unexpected deaths were natural rather than unnatural was 6.7 (95% confidence interval [CI], 2.8-19.4), Eighteen families had 2 sudden infant death syndrome (SIDS) deaths; the relative risk of SIDS recurring was 5.9 (95% CI, 4.1-8.1). The ratio of the rate of natural sudden unexpected infant deaths among CONI infants to that in the general population was at least 5.71 (95% CI, 4.1-7.7). The investigators conclude that, in most cases, a second or third sudden unexpected infant death within a family is the result of natural causes.