Bartholin’s cyst is a fluid filled sac that develops in the Bartholin’s glands. The Bartholin’s glands are located on each side of the opening of the vagina. These glands are responsible for secreting fluid that provides lubrication for the vagina. The Bartholin’s glands can sometimes become blocked, which causes fluid to get backed up into the glands. As a result, a cyst forms called a Bartholin’s cyst. A Bartholin’s cyst is mostly painless but can swell. In some cases, a Bartholin’s cyst can become infected if bacteria gets trapped in the cyst.