While there isn't one sleeping position for kids that reigns supreme, resting on your back has been regarded as the healthiest sleep position. That's because it puts the least amount of pressure on your lumbar spine. Side-sleeping is considered the next healthiest, helping to aid in digestion and relieve heartburn. And while many kids find stomach sleeping to be the most comfortable, know that this face-down position can lead to back or neck pain since the spine is more likely to fall out of alignment.Be sure to select a mattress that best fits your child's sleeping position, which is the easiest way to ensure a comfortable, healthy night of rest.