The odds are pretty good that you sleep like a baby. Either because you’ve found a sleep position that works for you or because you literally sleep in the fetal position, which is the most popular pose for slumbering, according to the National Sleep Foundation (NSF).

NSF says 41 percent of adults sleep this way, compared to seven percent passing out on our stomachs, 15 percent on our sides (which some studies say is ideal) and eight percent on our backs.

Curling up like a fetus makes evolutionary and biological sense, as the position protects all of our vital organs and it’s obviously how we hung out in the womb for many months. It’s also a good position for sleeping while pregnant, which is pretty interesting.

But the NSF says it’s not ideal for getting a good night’s sleep for the rest of us. That’s because it can cause breathing problems and sore joints in the morning.

Ideally, the sleep health research organization says we should all be sleeping on our backs because it allows the head, neck and spine to relax in a neutral position. It’s also better for dealing with acid reflux.

One big caveat, though, is that back-sleeping can be dangerous for those who suffer from sleep apnea and it might also endanger your domestic partnership situation as it sometimes worsens snoring.

Still, NSF says sleeping facing the sky is “by far the healthiest option for most people.”

Yet less than one-in-ten of us actually do it, so what gives?

Well, most likely it’s that back-sleeping isn’t super-comfortable for a lot of us. You can try it tonight and see for yourself. However, there is one other factor that I and a number of my friends have experienced that might also be part of the explanation.

The nightmares are the worst.

From particularly vivid dreams to terrifying cases of sleep paralysis, the truly freaky ones always seem to happen while sleeping supine. At least that’s what it seems like from my experience and the very informal collecting of anecdotes I’ve done over the years.

Turns out, thought, that there is some research to back up the notion.

“Studies have shown that people who sleep on their backs experience more nightmares and find it harder to remember their dreams,” says Calvin Kai-Ching Yu of Hong Kong Shue Yan University.

When it comes to sleeping, if you can’t bring yourself to put your back into it, the NSF says sleeping on your side is the second-best option. But if you’re like me, you’ll just take whatever you can get.