A hot mess. There’s no better way to describe the current state of the baby carrying industry. New parents doing their own online research on carriers will find an overwhelming number of choices and some very heated discussions—but very little scientific or medical research. As we said, a hot mess. So we decided to do our best to pull together all of the relevant facts, theories, and opinions in one place. Herewith, our complete guide to baby carrying.

First things first. Wraps, slings, and soft-structured carriers. What’s the difference?
“Though soft-structured carriers, slings and wraps all serve the same primary function—to carry your baby on your body and leave your hands free—they are all built differently,” explains Onya Baby creator Diana Coote. “A wrap is a long piece of fabric, measured in meters. There are as many ways to tie a wrap as there are parenting styles. Both woven (non-stretch) and knit (stretchy) wraps are available, each with its own set of pros and cons.

A sling is a simple, one-shouldered baby carrier that is essentially a loop of fabric folded lengthwise to form a pocket. The wearer places the sling on one shoulder and the baby in the fabric and they’re ready to roll. There are two types of slings: ring slings, which offer adjustability for more than one wearer, and pouch slings. Some pouch slings are adjustable, but most are not and must therefore be properly sized for the wearer.

A soft-structured carrier (SSC) is a modern take on traditional Asian-style baby carriers, in particular the Mei Tai and Onbuhimbo—except an SSC uses buckles instead of ties. The beauty of the buckles is that it’s much simpler and quicker to put on a SSC while still retaining the wide range of adjustability for many different sizes of babywearers.”

Got it. Is one category safer than the others?
For starters, “None is meant for carrying premature or low birthweight babies,” says pediatrician and AAP Fellow Dr. JJ Levenstein. But parents need to be especially careful with slings. “The U.S. Consumer Product Safety Commission (CPSC) is advising parents and caregivers to be cautious when using infant slings for babies younger than four months of age. In researching incident reports from the past 20 years, CPSC identified and is investigating at least 14 deaths associated with sling-style infant carriers; twelve of the deaths involved babies younger than four months of age.

As for soft carriers and wraps, the CPSC has received reports of two fatalities associated with soft carriers—both due to positional asphyxia (one child upright in the carrier with respiratory distress, the other face-down when a parent fell asleep with the carrier on and the baby still in it); and 91 non-fatal incidents due to falling from the carriers—caused by large leg holes permitting the egress of the baby, failure of buckles or straps, or the adult falling with the baby in the carrier, sustaining an injury.”

What are the most important things to keep in mind, when choosing a carrier?
“Make sure the carrier hasn’t been recalled and is in good shape,” advises our gear guru, Jamie Grayson of the Baby Guy NYC. “The carrier should be free of defects and holes, and should have nice linear stitching with consistent stitches,” adds Boba co-founder Elizabeth Antunovic. “Test the buckles so they click when you put them together. No rough fabrics or strange odors.”

BabyBjorn advisor Dr. Amanda Weiss Kelly (Division Chief, Pediatric Sports Medicine, UH Rainbow Babies and Children’s Hospital) also points out that, “It should be safe and easy for one person to take on and off by themselves. Parents should also pick a carrier that is comfortable for them.” Ergobaby founder Karin Frost agrees saying, “Parents should look for a carrier that distributes the weight of baby evenly on their hips and shoulders, which will allow for a much more comfortable carry.” Frost also suggests finding a carrier that will fit everyone who will be carrying the baby regularly; that has adjustable soft padded shoulder straps and waist belts that are fairly wide and don’t twist; that is adjustable to baby’s growth; and that is machine washable.

But according to Coote (Onya), the most important safety aspect is “making sure that the manufacturer is in compliance with all safety regulations and that the carrier’s design has been tested to passing in a third-party certified testing facility. Because this is now law, all carriers on the market fit this criteria, unless you purchase from a home-based manufacturer.” Dr. Levenstein concurs, saying, “Don’t buy one used or second hand.” Levenstein also adds that all babies should meet the specific weight requirements outlined by each manufacturer. “Don’t purchase a carrier meant for an older child, and assume your baby will “grow into it”—as the leg holes, support, and structure may not be safe for a younger baby.”

Okay. Now for the real hot buttons: Crotch dangling and hip dysplasia.
“Crotch-dangling” is a term that came about in the late nineties,” says Grayson. There was a paper written by Rochelle L. Casses, D.C., in which she stated that incorrect baby wearing in a crotch-dangling-type-carrier could lead to spondylolisthesis (a condition of the spine whereby one of the vertebra slips forward or backward compared to the next vertebra) and possibly hip dysplasia. But as it turns out, there is no scientific evidence that hip dysplasia or spondylolisthesis is caused by carriers of this type. Spondylolisthesis and hip dysplasia are much more problematic and prevalent in countries where babies are swaddled tightly at the hips.”

That’s right, says pediatric orthopedic surgeon Dr. Timothy Radomisli of Mount Sinai Hospital in New York. “There is absolutely no scientific basis for concern about baby carriers. I’ve never seen any baby carrier injuries. In 20-something years. Never heard of it.” But what about this diagram that’s long been posted on the International Hip Dysplasia Institute website, illustrating that BabyBjorn-style carriers are not recommended? “I think the diagram is pure conjecture,” states Radomisli. “To validate it, you’d need an outcomes study comparing babies who wore different carriers. I’ve never seen a baby develop dysplasia from a carrier. Current sonographic studies suggest dysplasia is congenital, not developmental.” Yep. “If a baby has the opportunity to flex his legs at the hip, rather than his legs being “bound” together (as in tight swaddling) he is not in a position to increase risk of hip dysplasia,” chimes Dr. Levenstein. (Editors’ note: we were hoping to better understand IHDI’s position on this, but unfortunately director Dr. Price told us, “We’d rather not make an additional statement.”)

“A baby carrier can’t cause hip dysplasia, but improper leg positioning is far from ideal for babies who have it,” says Antunovic (Boba). Well, yes. We understand that it may not be an ideal position for a baby born with hip dysplasia. But what about for healthy babies? “There is no risk for an unhealthy or uncomfortable pressure on the child’s crotch in carriers sometimes referred to as “crotch danglers,” states Dr. Kelly (Bjorn). “A baby’s center of gravity (larger head and shorter limbs than an adult), body proportions, and low weight, work together with carefully designed carriers that ensures proper support of the head, neck and back to evenly distribute baby’s weight. The only baby carrying practice that has been associated with aggravating hip dysplasia is tight swaddling and papoose-style carrying, where the child’s hips cannot move. All baby carriers, including front-facing carriers, keep babies hips in the abducted position, allowing for free movement of baby’s hips.”

Well, it may not be dangerous, but it certainly isn’t optimal says Ergobaby Chief Science Officer, Henrik Norholt. “To have all the weight of the baby placed on the groin and the legs left dangling straight down is simply not optimum from a physiological developmental point of view. The best position to promote a healthy development of spine and hip is the spread squat position or “frog-leg position.” In fact, this is the very position that babies are placed in a brace when hip dysplasia has been diagnosed, because the position stimulates the optimum growth of the hip joints.”

Hot button topic number two: inward-facing or outward-facing?
Everyone that we interviewed agrees that babies should face inward until four to six months of age, when a baby has head and neck control. So, let’s talk about ages six months and up. Why the backlash against outward facing carriers?

Well, for one thing, it’s awkward, says Antunovic (Boba). “The baby is not embracing the wearer, which makes for an awkward load. The wearer usually compensates by arching his back and holding his pointer fingers out for the baby to grasp so that the he or she doesn’t slump forward. And if the baby is facing forward, weak infant abdominals cause your baby’s back to arch, leaving her legs, hips, and pelvis further unsupported. When you walk, your baby then takes in the force of the movement, and the weight of his own body on an arched spine. Although no formal studies have been conducted on the relative positioning of babies in carriers, I’m confident that any extra pressure on developing hips and spines is undue.

Dr. Barbara Minkowitz, Medical Director of Pediatric Orthopedics at Atlantic Health Systems, agrees. “When the baby is facing away from the wearer, the baby can not be held in the “human position,” which is optimal for hip development and child support. Human position is when the child’s legs and body are supported to allow flexion (bending at the hips and knees) and abduction of the legs (spreading of the legs apart). While achieving this position in the upright position, the back is automatically supported and able to maintain its natural contour in the sagittal plane or natural alignment on side view.”

We also hear a lot of “overstimulation” claims with regard to outward-facing. Absolutely, says Coote (Onya). “Over-stimulation of the baby is a concern. It doesn’t allow the baby to make the choice to turn away and take a break. Many times, when a baby gets tired, he will bury his head in his mother or father’s breast, getting comfort, warmth, quiet, and the ability to shut out the stimulation of the world around him. Forward-facing carries remove this option.”

However, “It’s important once children are able to recognize that things are going on in the outside world, to allow them to interact with that world at their level of comfort,” says Dr. Kelly (Bjorn). Yes, a little stimulation is okay explains Dr. Levenstein: “Once older, facing outward provides appropriate environmental stimulation for baby as his distance vision and interest in the outside world is “fed” by turning outward when alert and awake. In addition, if a baby is facing outward and is uncomfortable, a parent is close enough to hear the fuss/crying, and that should signal to the parent to change position.” For an even better understanding of over-stimulation risks, we turned to the developmental Ph.Ds at Seedlings Group. “Keep in mind that infants communicate with their caregivers quite beautifully and we are hardwired to respond,” replies Dr. Aliza Pressman. “If an infant is overstimulated he or she will cry and express distress. If the infant is not distressed, then all is well. Especially after six months of age. It’s important to keep in mind that all of the research on kangaroo care applies to newborns, particularly those who were born preterm.”

Still, Ergo believes inward is best. “Sometime during the baby’s first year, most babies placed in the front inward facing position will begin to turn their head to get a better view of the action taking place behind them,” says Norholt. “Given the flexibility of a baby’s neck and the wide zone of vision that eye movement allows for, the baby will in fact be able to take in quite a lot of the surrounding environment. If this solution works for you, and your baby is content, we strongly suggest that you keep your baby in the front inward facing position.”

Of course, as with most parenting concerns, the best strategy is to take cues from your child. “It’s up to parents to exercise common sense,” says Grayson. “If you think your kid is getting overstimulated while looking out, simply turn him around.”

Anything else parents should keep in mind when using a carrier?
“Be sure to keep the baby’s face visible,” advises Grayson. “Keep the airway open—be wary of the “chin-to-chest” position, which can cause respiratory issues. And be careful of extra fabric covering your child’s mouth and nose.” Frost (Ergo) adds that baby should be “close enough to kiss” and high on the wearer’s body. Take it easy, says Antunovic (Boba). “Walking is great exercise, but save the jogging, jumping, or high-impact endeavors for when you’re not wearing your baby.” Antunovic also reminds parents to watch baby’s temperature in hot weather and to check the carrier prior to each use to be sure that there are no signs of fraying, tearing, seam-splitting or cracked or broken buckles.”

But at the end of the day, “the single most important predictor of positive maternal and child bonding is maternal mental health,” reminds Dr. Pressman (Seedlings). “It’s what makes each individual dyad (mother-child pair) work together in their own unique ‘dance’ and nobody else need opine about it.”

Amen to that.