If gas enters the vagina and then is discharged, it is often caused by the following clinical reasons: 1. During childbirth, the dewlap presses on the pelvic floor, causing the muscles of the pelvic floor to drop in tension, resulting in a relaxation of the vaginal wall and causing a gap between the front and back walls of the vagina, which cannot fit together, and the air enters the vagina along the gap and is then discharged outside the vagina, forming a sound similar to a fart. 2. In thin women, the muscles and fat of the pelvic floor are not plump, resulting in the front and back walls of the vagina not being able to close together, resulting in the entry of air. 3. Due to the old laceration of the perineum, air can easily enter, and in this case, it is recommended that perineal repair surgery be performed.