Q. Our baby girl likes to sleep on her stomach, even if you put her on her back or side. She's 5 months old and has been sitting and rolling since 4 months. Should we worry about sudden infant death syndrome (SIDS)?

A. Even though SIDS is high on a parent's worry list, it is actually a rare tragedy, occurring in approximately 1 out of every 1,000 babies. SIDS most commonly occurs between 2 and 4 months of age, and after 6 months the chances of an occurence are even more unlikely. So, your baby is just about past the age where you need to worry.

It sounds like you have a precocious baby who will assume her favorite sleeping position regardless of how you put her to sleep. Even though back-sleeping has been proven to be the safest sleeping position, some SIDS researchers believe that babies will intuitively try to find their own individual safest position. That sounds like what your baby is doing.

Up until the past few years, it was believed that there was little that could be done to reduce the risk of SIDS, however new insights have shown that there are, in fact, several major ways parents can protect their children:

1. Put your babies to sleep on her back, not her tummy. Worldwide "Back to Sleep" campaigns over the past 10 years have resulted in a fifty-percent decline in SIDS rates. It is unknown why back-sleeping reduces the risk of SIDS, yet researchers believe that arousability from sleep -- an infant's built-in protective mechanism -- works better for babies who sleep on their backs rather than their stomachs. Also, babies' breathing systems seem to work better in the back-sleeping position. When sleeping facedown a baby may press her head into the mattress and form a pocket of air around her face, leaving her to rebreath exhaled air with diminished oxygen.

2. Provide your baby with a safe sleeping environment. Avoid putting your baby to sleep on sinky, unsafe surfaces such as beanbags or couches.

3. Breastfeed your baby. SIDS is less common in breastfed babies for several possible reasons. One theory is that nerves around the respiratory control center may be better developed in breastfed babies because breast milk is rich in omega-3 fatty acids (especially DHA). These provide vital nutrients for myelin, the insulating sheath around nerves that help impulses travel faster. Breast milk is also kinder to tiny airways as babies are not allergic to mother's milk, and breast milk also contains immune boosters that fight against chest infection. Another perk is that gastroesophagel reflux (GER) -- which can often lead to stop-breathing episodes -- is less severe in breastfed babies. Finally, both experience and research has shown that breastfed babies sleep differently then bottle-fed ones. Breastfed babies awaken more frequently to feed, mainly because human milk is digested more quickly than formula. Could this easier arousability also "teach" babies to arouse from sleep when they have a need for air? Dr. James Mckenna, director of the Mother Baby Sleep Labatory of the University of Notre Dame has thoroughly studied arousability of breastfed babies, and has concluded that getting babies to sleep too deeply, too early, may not be in their best biological interest. In essence, sleeping deeper does not necessarily mean sleeping safer.

4. Don't smoke around your baby, postnatal or prenatal. Exposure to cigarette smoke greatly increases the risk of SIDS, possibly because nicotine and other poisonous substances in smoke harms the respiratory control center in your baby's developing brain.

I don't recommend using wedges to prop your baby on her side or back. These have never been proven safe or effective and are unlikely to work for a baby with such advanced rolling skills. Try to encourage back-sleeping by putting your baby down to sleep on her back, yet allow her to assume her own favorite sleeping position. Rest assured that SIDS is rare, especially at 6 months, when nearly all babies go to sleep each night and wake up just fine.