July 22 (HealthDay News) -- Many infant deaths in the 19th century that were labeled as infanticide or neglect may actually have been sudden infant death syndrome (SIDS), a U.S. study suggests.

Historically, the sudden death of an apparently healthy baby would have been attributed to accidental smothering or overlaying by either bedding or a co-sleeper, according to background information. Smothering deaths were believed to be caused by parental neglect, while infant-adult bed sharing was regarded as proof of parental incompetence.

The analysis of data from the U.S. Federal Mortality Schedule from the years 1850 to 1880 revealed that, like SIDS, smothering and overlaying deaths occurred primarily during the second to fourth month of the baby's life, were more common in the late winter months and among boys, and death rates were higher for black infants.

"The study strongly supports the hypothesis that these infant deaths represent empirical evidence of 19th-century SIDS mortality," concluded Dr. Ariane Kemkes, an independent researcher in Scottsdale, Ariz.

The study appears online in the journal Human Ecology.

SOURCE: Human Ecology, news release, July 2009