The Back To Sleep campaign was introduced in the 1990's as a way to reduce the number of unexplained infant deaths (SIDS) and since back sleeping has become commonplace the number of SIDS deaths has decreased (although it actually started decreasing 10 years BEFORE back sleeping started to be heavily promoted).  The research actually shows that breastfeeding and zero exposure to cigarette smoke are even bigger ways to reduce SIDS risk.  Telling women that formula feeding and smoking is connected with an increased risk of SIDS isn't a very popular approach though so they went with the Back To Sleep campaign as it is much more palatable to the public.  While the number of SIDS deaths has decreased since Back To Sleep was implemented, there has also been an increased awareness of the risks of formula feeding and smoking and to my knowledge no research has yet teased out whether Back Sleeping IS actually what is leading to a decrease in SIDS risk.

Which isn't to say that if you formula feed and smoke your baby is going to die!!! In reality, SIDS only accounts for a very small number of infant deaths each year.  There are also HUGE discrepancies with how infant deaths are recorded - what one coroner rules as SIDS, another might rule as asphyxiation for example.

So what about tummy sleeping then?  First we have to distinguish between tummy sleeping and UNSAFE sleeping because they are not necessarily the same.  Whether the baby is on their back, tummy, or side, they need to be in a safe sleep environment.  A safe sleep environment is: 
Clean. 
Clear of clutter. 
Contained (ie baby can’t fall out or get wedged somewhere).
Firm. 
Flat. 
Good air circulation. 
Moderate temperature.  
Within arms reach of mom (ideally).


 A sofa?  Not a safe sleep space. 
A pillow top mattress? Not a safe sleep space.  
A stuffy hot room?  Not a safe sleep space.  
A crib with bumper pads and quilt and stuffed animals and blankets? Not a safe sleep space. 
A mattress that smells strongly? Not a safe sleep space. 
With siblings, pets, or other kids? Not a safe sleep space.
On an adult bed with an obese parent? Not a safe sleep space.  
On an adult bed with a parent whose ability to wake up is compromised? Not a safe sleep space.  
On an adult bed with a pile of pillows and blankets? Not a safe sleep space.  

Babies DO die more often when they are left to sleep in unsafe spaces.  Babies are generally less at risk for SIDS or other sleep-related causes of death  when SAFE sleep guidelines are followed.

If your baby seems to do best as a tummy sleeper you’ll need to make sure that all the other safe sleep guidelines are being followed.  

Part of the problem with tummy sleeping comes when a baby isn’t used to it.   A baby who always sleeps on their back but is put on their tummy only rarely is at an increased risk of SIDS, as is a baby who side sleeps and rolls unexpectedly onto their tummy.  Some parents try to get around this with the use of sleep positioners or rolled up blankets on the sleep surface to keep the baby on their back or on their side but that is not recommended either as the baby can become dangerously tangled.

If you are going to choose to tummy sleep, you need to do so consistently, not just on occasion. Keep a fan in the room pointing over the sleep space so that fresh air is constantly circulating.  During naptimes check on baby frequently to make sure they’re doing ok.  At nighttime, baby should sleep within arms reach of mama as this allows their heartbeat and breathing and sleep-wake cycles to sync up. If desired, use something like an AngelCare monitor. 

Yes, there are risks.  But there are also benefits.  It’s a matter of deciding which risks/benefits you’re most comfortable with.

References, Resources, and Further Reading

Canadian Pediatric Society Safe Sleep Statement 2014

Health Canada Joint Statement on Safe Sleep 2012

Mother-Baby Behavioral Sleep Laboratory - Dr.James McKenna

Ask Dr.Sears: Tummy Sleep

Washington University - lack of experience with tummy sleeping & increased SIDS risk

Natural to the Core: Revisiting SIDS & Back Sleeping