Sleep Ranking: Eh, at least you're not sleeping on your face

Who/What It's Good For:
If you're pregnant, have heartburn or sinus issues (or simply can't sleep staring straight at the ceiling), it's best to sleep on your side. "The left side is best for heartburn or acid reflux, because the position keeps your stomach below your esophagus," says Dr. Breus. A side sleeping position also keeps your tongue from falling to the back of your throat, which causes you to snore. Pregnant women may find side sleeping can improve blood flow and the amount of nutrients being delivered to the baby, as well as reduce swelling in their hands, feet and ankles (of course a killer high heel obsession a la Kim Kardashian will probably undo all of those benefits).

Who/What It's Bad For:
The good news -- 75 percent of Americans sleep on their side, according to Dr. Breus, so although it's not quite as good as sleeping on your back, it's perfectly fine to continue snoozing on your side. The bad news: Dr. Day says side sleepers often get wrinkles or creases on the side they naturally turn to in sleep, getting a deeper crease on the side they favor. If you can't break out of the fetal position, Dr. Melamed recommends choosing a softer mattress. The mattress should help you avoid pressure points, but shouldn't be so soft that it doesn't properly support your neck.

Try This:
Because transitioning to another sleep position is so difficult, Dr. Breus says staying put sleeping on your side is perfectly fine. But if you simply can't settle for less than the optimum (sometimes our perfectionist can't help but kick in), proper pillow placement can help you transition to sleeping on your back. Many side-sleepers attempt to use pillows under their knees or on either side to keep them from rolling over, but this won't work as well as you'd imagine. "We often see that people will fall asleep on their back, and then roll over on top of these pillows meant to keep them on their back," says Dr. Breus. "Instead take couch cushions (the big ones you sit on) and put them on either side of your torso. These pillows are large enough to keep you on your back and won't easily roll out of position."