The Bartholin's (BAHR-toe-linz) glands are located on each side of the vaginal opening. These glands secrete fluid that helps lubricate the vagina. Sometimes the openings of these glands become obstructed, causing fluid to back up into the gland. The result is relatively painless swelling called a Bartholin's cyst. If the fluid within the cyst becomes infected, you may develop a collection of pus surrounded by inflamed tissue (abscess).