Is It Prohibited to Sleep on Your Belly?
Question

Why is it forbidden to sleep on one's belly? Is it forbidden for both men and women?
Praise be to Allah.The reason for the prohibition of sleeping on one’s belly is that it was forbidden by the Prophet (peace and blessings of Allah be upon him), who left no good thing but he told us about it and left no evil thing but he warned us against it. 
Ya`ish ibn Tihfah Al-Ghifari (may Allah be pleased with him) reported that his father said: “I stayed as a guest with the Messenger of Allah (peace and blessings of Allah be upon him) with those of the poor whom he hosted. The Messenger of Allah (peace and blessings of Allah be upon him) came out in the night to check up on his guests, and saw me lying on my stomach. He prodded me with his foot and said, ‘Do not lie in this manner, for it is a way of lying that Allah hates.’” According to another report, the Prophet (peace and blessings of Allah be upon him) prodded him with his foot and woke him up, and said, “Do not lie like this, for this is how the people of Hell lie.” (Narrated by Ahmad, Al-Fath Ar-Rabbani, 14/244-245; by At-Tirmidhi, 2798, Shakirs edition; and by Abu Dawud, As-Sunan, Kitab Al-Adab, 5040, Ad-Da`as edition. Also reported in Sahih Al-Jami`, 2270-2271)
This is a general prohibition that applies to both males and females, because the basic principle is that rulings apply to both sexes, except in cases where it is indicated that there is a differentiation between the two. 
For more details, please refer to the following answers: 1409 , 14033 , 104215 , 50010 , and 21388 .
And Allah knows best.