And according to Drs. Jodi Pike and Rachel Y. Moon of Children's National Medical Centre in Washington, DC, the cause of death in 85 percent of the cases was lack of oxygen.
In their analysis of these deaths, Pike and Moon also found that more than one third of the babies had been placed on their stomachs and one half was found on their stomachs. In 74 percent of cases, items such as blankets, pillows, and plastic bags were found in the bassinets.
Nine infants died in bassinets that were not functioning correctly, either from misuse or mechanical problems.
Between 1992 and 2000, the percentage of infants sleeping in bassinets doubled, to almost 20 percent, Pike and Moon note in a study published in The Journal of Pediatrics. Bassinets are most often used in the first two months of life, when more than 45 percent of infants sleep in bassinets, according to a 2007 study.
"The risk of sudden unexpected death in infants who sleep in bassinets can be reduced by following American Academy of Pediatrics guidelines," they write, including placing infants to sleep on their backs on a firm surface and keeping the bassinet free of blankets, pillows and other items.
"If parents plan to use a bassinet, they should make sure that it is in good repair and conforms to Consumer Product Safety Commission guidelines," Moon added in a written statement. The CPSC recommends that bassinets have a sturdy bottom with a wide base, smooth surfaces without protruding hardware, legs with locks, and a firm, snugly fitting mattress.
"Because six of the 53 infants were found with their faces wedged against the side of the bassinet," Pike and Moon suggest that a bassinet with sides made of an air permeable material might be safer.
In related research, Moon and colleagues reviewed the sleep sites of 708 mothers and their infants using data collected from several Women, Infant, and Children centres (WIC) in 2005 and found that roughly 33 percent of the mothers and infants were sleeping together.
Bed-sharing was more commonly seen among teen-age and African American mothers. However, close to half of the mothers reported that they slept in the same room but in a separate bed, a "reassuring finding," the researchers note.
"Approximately half of all sudden and unexpected infant deaths in the United States occur when an infant is sharing a sleep surface with someone else," the researchers write, and "the factors associated with bedsharing are also associated with sudden infant death syndrome (SIDS)."