Baby slings have been used to carry infants across the chest or back for thousands of years. There are lots of great reasons to use them. Research shows “sling babies” cry less and are more content, according to pediatrician William Sears, MD, author of “The Baby Book: Everything You Need to Know About Your Baby from Birth to Age Two.” Parents of fussy babies who try infant slings “say their babies forget to fuss,” he says in an article on his website.

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But consumer safety groups caution that if infant slings are used too early or the wrong way, they can be dangerous. At least 14 deaths associated with baby slings have occurred in the last 17 years, according to Consumer Reports, along with dozens of injuries. Here’s what you need to know.

#1. If your baby is under 4 months old, she faces a significant risk of suffocation.

In Salem, Oregon in 2010, Lisa Cochran’s 7-day-old son suffocated in an infant sling as Cochran was walking from a Costco store to her parked car. The grieving mother, who blamed the infant swing for her son’s death, was so bereft that she found herself unable to get out of bed, shower or even talk on the phone for weeks. It was too painful to venture outside, she told CNN, “because the first thing everyone asks is, 'How's the baby?' "

Suffocation is a “significant” risk for infants under 4 months of age in baby slings, according to the Consumer Product Safety Commission (CPSC). In fact, 12 of the 14 reported deaths from baby slings occurred in babies less than 4 months old. “In the first few months of life, babies cannot control their heads because of weak neck muscles. The sling's fabric can press against an infant's nose and mouth, blocking the baby's breathing and rapidly suffocating a baby within a minute or two,” the CSPS warns on its website.

“Additionally, where a sling keeps the infant in a curled position bending the chin toward the chest, the airways can be restricted, limiting the oxygen supply,” according to the CPSC. “The baby will not be able to cry for help and can slowly suffocate."

Unlike Consumer Reports, which has put baby slings on its list of “dangerous baby products to avoid,” the CPSC and Mayo Clinic say you can use the slings safely in babies older than 4 months of age, if you take the proper precautions.

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#2. Avoid slings with a design that pull baby into a fetal or curled position.

This can put pressure on your baby’s breathing passages even if her nose and mouth are clear. Even if you have a regular sling, check regularly to make sure baby hasn’t sunk down so far you can’t kiss the top of her head. Her chin should not be resting on her chest since this can interfere with normal breathing.

#3. Be wary of used slings.

That beautiful sling you saw at a yard sale or that your neighbor wants to give you may have been recalled for suffocation hazards. Others may have worn fasteners and stitching points. If you do choose to buy one used, check the model numbers against CPSC product recalls of infant slings .

#4. Never bend over with a baby in the sling.

Bend your knees rather than bending over if you need to reach for something low. If you lean over, the pressure of your body could hurt the baby. Also, she could slip free of the harness and fall to the ground. CPSC has logged dozens of injuries, including skull fractures, head injuries, bruises and scrapes that occurred when infants toppled out of a sling.

Related: How to Use a Baby Carrier Safely

#5. Check the hardware before putting your precious bundle inside.

Just as if you were about to rappel up a mountain, give the fasteners (if any) a tug to make sure they’re secure.

Steve Evans, MA, is an award-winning journalist with more than 20 years experience in daily news, investigative, health and business journalism. Among other jobs, he has served as managing editor of the Central Virginia Newspaper Group, as a senior writer for SNL Financial and as a staff writer for The Progress Index and the Richmond Times-Dispatch.