What Is a Corpus Luteum Cyst?

A corpus luteum cyst is a type of ovarian cyst (a small, fluid-filled sac). The corpus luteum itself is a vital, but temporary temporary endocrine structure. It forms from cells in the ovarian follicle wall during ovulation. This type of cyst happens when the corpus luteum continues to grow rather than break down as it typically does.

Also called a corpus luteal cyst, this condition often occurs during pregnancy. It can also appear at other times, primarily during the reproductive years.

What Is the Corpus Luteum?

Understanding the ovulation process can help explain how and why these cysts develop.

Your ovaries have thousands of follicles, which are little pouches that hold eggs. Once a follicle releases an egg during ovulation, it forms the corpus luteum—a short-lived structure that releases estrogen and progesterone, hormones that ready the uterus for implantation.

The breakdown of the corpus luteum helps to trigger menstruation. If conception occurs, the corpus luteum sticks around longer to produce hormones. The placenta will take over the function of progesterone production at around 12 weeks gestation.

Typically, the corpus luteum will disintegrate around 11 to 12 days after ovulation if conception does not occur and at between 7 and 9 weeks during pregnancy. However, sometimes, a corpus luteum cyst can develop on the ovary instead. When this happens the corpus luteum fills with blood and keeps growing rather than breaking down at the typical time. Usually, the cyst is benign, painless, and will eventually go away on its own.

Symptoms

In many cases, women who have a corpus luteal cyst do not experience any pain or other symptoms. In fact, a corpus luteal cyst will typically resolve on its own after a few menstrual cycles without a woman even knowing it was there.

The most common symptom in those who do take notice of a corpus luteam cyst is a slight twinge of one-sided pain or mild tenderness during the menstrual cycle. However, if there is some pain, it can mimic the type of pain associated with an ectopic or tubal pregnancy. Consult with your doctor or midwife if you have any pain you are concerned about.

Note that you also may have a corpus luteum cyst and not be aware of it. Many people have them without knowing since they are often painless and are typically only detected if an early ultrasound is given.

Identifying Corpus Luteum Cysts

Corpus luteal cysts are typically diagnosed with a transvaginal ultrasound, also called an internal ultrasound. A transvaginal ultrasound allows for a closer view of pelvic structures than a pelvic ultrasound offers. However, these cysts may also be seen using a pelvic ultrasound, which is a non-invasive diagnostic ultrasound tool that's placed on top of the abdominal skin.

In a transvaginal ultrasound, your provider inserts a wand called a transducer into your vagina. The device emits sound waves that produce images of the inside of your body and projects them on to a monitor.

Corpus luteum cysts vary in size but are usually between 2 and 6 centimeters. They are usually not a cause for concern. However, these cysts can occasionally lead to complications, which are typically unrelated to pregnancy itself.

There may be more opportunities to spot a corpus luteal cyst in a woman who's expecting, simply because they're usually having routine imaging as part of their prenatal care. For this reason, these cysts are diagnosed more often during pregnancy.

Your doctor or midwife may want you to have a follow-up ultrasound to check on the cyst if you continue to have symptoms. Otherwise, unless pain or other symptoms necessitate treatment, no follow-up is typically needed.

Risk Factors

Anyone can get corpus luteum cysts, though they are more likely to develop in women taking medication to induce ovulation, like Clomid (clomiphene). These medications, which manipulate hormones in order to stimulate ovulation, are usually prescribed by a doctor or midwife for women experiencing fertility problems and for those with polycystic ovary syndrome (PCOS).

It's important to remember that since the corpus luteum is a normal part of the menstrual cycle, the type of functional ovarian cyst associated with them can also develop when you are not pregnant. You can also develop one even if you are not taking, or have never taken, medication to treat infertility.

Additionally, the following risk factors put you at greater risk of developing a corpus luteum cyst:

• Endometriosis
• Hormonal imbalance (this may be related to fertility treatment)
• Pelvic infection
• Pregnancy
• Prior corpus luteum cysts

Having had a corpus luteum cyst in one pregnancy does not necessarily mean you will develop one in another pregnancy. However, it is more likely. Additionally, if you have risk factors, such as a hormonal imbalance or endometriosis, then you're more likely to have a cyst again in a subsequent (or first) pregnancy. Additionally, sometimes the cause of a corpus luteum cyst is unknown.

Treatment

A corpus luteum cyst is usually not harmful. The cysts do not typically cause any complications during pregnancy, especially when they're discovered during the first trimester. If the cyst continuing to grow or worsen, surgery may be required to avoid the risk of miscarriage.

Occasionally, the cyst will rupture. Pain may increase when this happens but tends to subside quickly. Pain medication and rest may be indicated. Less frequently, a corpus luteum cyst can cause the ovary to twist (torsion). This can be very painful and may require surgery to prevent further injury of the ovary.

A Word From Verywell

While it may feel unsettling to learn you have an ovarian cyst, corpus luteum cysts usually do not cause pain or complicate pregnancy or birth. Also, they rarely require any treatment.