Ovarian cysts are fluid-filled sacs that develop on the ovaries, and they are not uncommon in women. Most cysts will go away without any treatment.
The corpus luteum is a functional cyst, which forms after ovulation. The corpus luteum produces progesterone and estrogen to help prepare the uterus for pregnancy. Normally, if conception does not take place, the corpus luteum diminishes.
Sometimes, however, the corpus luteum does not diminish like it should and it enlarges. It does not typically require treatment, and usually will go away after a few weeks. (Before fertility treatment, your doctor may order an ultrasound to check for these kinds of cysts. If there is one, treatment will be delayed until the cyst disappears.)
Endometrioma cysts, also known as “chocolate cysts," are cysts that appear on the ovary and are filled with old blood. These cysts may cause pelvic pain and interfere with ovulation. They are caused by endometriosis.
Multiple, tiny cysts that appear on the ovaries may be a sign of polycystic ovarian syndrome (PCOS). They can cause the ovary to be enlarged and a hardened crust-like cover to form over the ovary, interfering with ovulation and the ability to get pregnant.