Question:
May a woman lie in a prakdan position (on stomach or on back)?
Answer:
There are two issues with lying on ones back. Not going to sleep on one’s back or stomach as not to cause a loss of seed, which would not apply to women. Additionally, when a person says kriyas shema it is not respectful to talk to Hashem this way, which would seem to apply to women. if it is difficult to sit up one may lay slightly to the side, which is not considered prakdan.
Best wishes
Sources:
פשוט, וכן מצאתי בס’ עבודת אהרן דך י”ב. בס’ נכתבים אות ל”ד.