Bundle baby up...
but not too much
When it's this cold outside, be sure that your baby is bundled up right for bedtime.
Dress baby for warmth and comfort
You don't have to layer warm fleece sleepers, as Baby may end up getting too hot and thus too uncomfortable to sleep. But feel free to layer a light sleep 'n play outfit over a onesie. Then, if you're still swaddling, wrap baby up in his swaddle blanket. If not, consider a "sleep bag" for an added layer without using a blanket, which baby could become ensnared in as he moves about during sleep.
Ensure that the pajamas, onesies and swaddle blanket or sleep bag are 100 percent cotton or another breathable material that won't cause baby to sweat in the night. Keep in mind the rule of thumb — dress baby in one more layer of clothing than an adult would be wearing in that same temperature.
Yes, it's cold outside. But it's not like Baby's sleeping out there — so don't go overboard bundling him up. Focus on the interior temperature of his room and keep in mind that he won't be able to sleep comfortably if he's too wrapped up or too warm. An ideal temperature to keep Baby's room (and your own, while we're at it) is actually a little on the cool side — about 68 degrees F. If that feels too chilly to you or your baby's skin feels cold to the touch, crank up the heat up a few notches.
However, it is very important not to allow your baby to overheat during nap or sleep time as it can actually put Baby at risk for SIDS. According to KidsHealth, research suggests that a baby who gets too warm could go into a deeper sleep, which makes it more difficult to wake him — making him susceptible to SIDS. The site suggests, "Keep the room at a temperature that feels comfortable for an adult in a short-sleeve shirt."
Research exists showing that use of a fan can actually reduce your baby's risk of SIDS. In 2008, a study by the Kaiser Permanente Division of Research found that "infants who slept in a bedroom with a fan ventilating the air had a 72 percent lower risk of [SIDS] compared to infants who slept in a bedroom without a fan." If you're using a fan in Baby's room during the winter months, ensure that it is on the "winter" setting or is rotating clockwise (in most cases) to distribute heat from your home's central heating unit versus circulating cold air Baby's way.