Don't cover babies with extra blankets or clothes during winter because of the risk of SIDS (sudden infant death syndrome).

That advice comes from the National Institute of Child Health and Human Development (NICHD), a branch of the National Institutes of Health (NIH).

The number of infants who die of SIDS rises during the winter, notes an NICHD news release.

During these colder months, parents often place extra blankets or clothes on infants, hoping to provide them with more warmth. In fact, the extra material may actually increase infants' risk for SIDS, states the release.

Unless there's a medical reason not to, infants should be placed on their backs to sleep, on a firm mattress with no blankets or fluffy bedding under or over them, the release continues.

If a blanket is used, it should be placed no higher than the baby's chest and be tucked in under the crib mattress. The baby's crib and sleep area should be free of pillows and stuffed toys, and the temperature should be kept at a level that feels comfortable for an adult, states the release.

About SIDS

SIDS is the sudden, unexpected death of an infant who is less than 1 year old with no explanation for the baby's death after a thorough investigation.

Although rare, SIDS is the leading cause of death in infants between 1 month and 1 year of age. Every year, about 2,500 U.S. babies die of SIDS, according to the NICHD.

Most SIDS cases happen when babies are 2 to 4 months old, states the NICHD.

SIDS cases have dropped by more than half since SIDS education campaigns began more than a decade ago. However, SIDS is still more common among minorities than among whites, notes the NICHD.