Dear Doctor: Our daughter is 5 months old, and we always put her to sleep on her back. Lately, when we check on her, she's on her stomach. Should we be keeping an eye out and positioning her on her back again when that happens? Dear Reader: First, congratulations on your daughter hitting an important developmental milestone! Rolling over, which typically occurs anywhere from the ages of 4 to 6 months, is an important part of a baby's development. It's one of the first steps on the journey to your baby becoming mobile. Your daughter is gaining in both muscle strength and coordination; that gentle rocking from side to side that you have noticed has now become forceful enough that she is able to flip herself over. It's true that since 1994, the American Academy of Pediatrics (AAP) has recommended that parents put babies to sleep on their backs. This is to prevent sudden infant death syndrome (SIDS), the unexpected and unexplained death of an apparently healthy baby, often during sleep. The exact cause of SIDS remains unknown. However, researchers believe that it may occur when an infant's airway becomes blocked for some reason, and the part of their brain that would normally wake them up isn't developed enough yet, or isn't functioning properly. The "Back to Sleep" campaign, which began in 1994 to urge parents to place sleeping infants on their backs, has helped significantly reduce SIDS deaths in the United States. Here's the good news: Now that your daughter is able to turn herself over unaided, her brain has developed enough that she will shift position should she experience any problems with breathing. The National Institutes of Health recommend -- and we agree -- that you should continue to start her out on her back when she's going down for a nap or for the night. Should she turn over during her sleep, it's fine -- you don't need to reposition her on her back. There are a few other simple precautions you can take to ensure a safe and comfortable sleep environment for your infant. First, make sure she's lying on a firm mattress with a fitted sheet. Don't cover her with loose bedding, such as a sheet, blanket or quilt. Instead, dress her in just enough sleep clothing to keep her comfortable throughout the night. Although she may need to fall asleep with her favorite pillow or stuffed toy, once she's nodded off, keep her bed clear of them and other soft objects. Overheating has been suspected to play a role in SIDS, so it's important that your baby's bedroom remain at a comfortable temperature. If your sleeping baby's chest feels hot to the touch, or if they're sweating, they may be too warm. To stave off potential problems, it's recommended that babies sleep in their parents' bedroom -- in their own crib or bassinet, not in the parental bed -- until they're at least 6 months old. Source