Risk of sudden infant death syndrome in subsequent siblings.

To determine the risk of recurrence of sudden infant death syndrome in families, we studied 251,124 live births by linked birth and death certificates from Oregon for a 10-year period. We found five recurrences among 385 subsequent siblings, for a rate of 13/1000 live births and a relative risk of 6. When the recurrences were adjusted separately for birth order and maternal age, the risk was still five times that expected (p less than 0.001). Families with infant deaths from causes other than sudden infant death syndrome had similar recurrence rates, suggesting that the phenomenon was not specific to sudden infant death syndrome. The overall mortality rate for subsequent siblings after a sudden death event totaled 20.8/1000. We believe that a risk of 2%, although small in the design of studies of infants at risk for sudden infant death syndrome, is not trivial in the counseling of parents.