The Back Sleeping Position
By far the greatest position for spine and neck health, as the back is straight and not forced into any contortions. This sleeping position also favors the mattress the most as it allows it to do it's job of supporting the spine. Ideally you'd be sleeping on your back without a pillow as this leaves your neck in a neautral position, however you can get away with one or two, just remember too many pillows can result in neck pain and make breathing more difficult.
Snoring! You probably just shuddered if you're a victim of your partner regularly doing so. Being led on your back forces your tongue to collapse into the airway creating a blockage which obstructs breathing and creates the oh-so joyful noise.
The Side Sleeping Position
Whether you chose the fetal position or lying straight on one side, this is the most popular sleeping position. Sleeping on your left side can ease heartburn and acid reflux, doctors also encourage side sleeping for pregnancy because sleeping on your back can lead to fainting due to too much pressure on your lower back, and sleeping on your stomach whilst pregnant is a no for obvious reasons.
If you're a side sleeper you've definitely had this problem more than once - the dreaded dead arm! Some avoid this by wrapping their arm behind their head, this can occasionally result in aches and pains in your muscle and nerves. Resting your head on one of your arms can result in painful pins and needles. In this position the shoulder also takes a lot of your weight, which in the long run (especially if you're a little heavy) can constrict your neck and shoulder muscles.
The Stomach Sleeping Position
The only thing considered good about sleeping on your stomach is that it eases snoring. Not looking good for any fellow stomach sleepers!
Widely regarded as the worst sleeping position, stomach sleeping can flatten the natural curve of your spine which will result in back pain, sleeping with your head turned to one side also places strain upon your neck, too.