In Buteyko Breathing Technique, one thing we emphasis besides the mouth taping is sleeping on your side, as sleeping on the side can help reduce our breathing volume. There are also many other studies that supports side way sleeping for various health benefits; this article from the New York Times discusses side sleeping benefit for the pregnant women.
If pregnant women in poor countries were advised to sleep on their sides, many stillbirths might be prevented, a new study suggests.
A graduate student’s summer project, the study is small — it included only 220 women interviewed about their sleep habits just after giving birth in one hospital in Ghana.
But because Ghana has such a high rate of stillbirth, said Louise M. O’Brien, the professor at the University of Michigan’s Sleep Disorders Center who oversaw the project, by Jocelynn Owusu, the conclusion seemed clear: If pregnant women avoid sleeping on their backs, 25 percent of all stillbirths in poor countries might be prevented.