Is it safe for newborns to sleep in? Can they breathe properly?

Of course! What makes a sling safe to sleep in is positioning the baby correctly and wearing and using your sling and it's fabric right. Your baby should never lay curled up with his/her chin close to their chest because this restricts their airway in part. A HugaMonkey has the pouch seam where the baby's bum should always rest. When using that seam as the guide the baby is positioned upright, with his face exposed to the air and his head up. With your baby in this position you can rest assured that his spine and back are in the right position to breath well.    There were some slings in the news that were recalled recently that had no positioning guide and the baby was left just laying flat inside, with all of the pressure on the center of the baby's back. That pressure is one cause for the infant to curl its head toward its chest and not breathe properly. Take a look at one of the models off our home page. You'll want your baby's head above your bustline when wearing your sling so that it is easy to see and hear your baby. Also, part of wearing your sling correctly is wearing the right size so that your baby is positioned right. You'll know your sling is too big if your baby is swinging around your hips with the pouch feeling too large.  Now dealing with fabric. There was one model sporting the mesh sides on the recalled slings. The majority of the recalled slings, however, were solid walled and made of three layers of fabric. And in many models the outer fabric was a thick velour or a synthetic nylon blend, both of which are not at all breathable. The HugaMonkey sling has just a single layer of 97% or 100% cotton - very breathable. With any sling, make sure that your sling fabric does not drape across your baby's face.