What To Know About Corpus Luteum Cysts During Pregnancy

A corpus luteum cyst is a type of ovarian cyst, which is a small, fluid-filled sac in the ovary. The corpus luteum itself is a temporary endocrine structure that naturally forms after ovulation. Corpus luteum cysts occur when the corpus luteum continues to grow rather than break down as it typically does at the end of the menstrual cycle.

Also called a corpus luteal cyst, this condition often happens during pregnancy, but can also appear at other times, primarily during the reproductive years. Here's what to know about corpus luteum cysts, including symptoms, diagnosis, risk factors, and treatment.

What Is the Corpus Luteum?

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

Your ovaries have thousands of follicles, which are little pouches that hold eggs. Once a follicle releases a mature 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 continue producing hormones to support the pregnancy until the placenta takes over at around 12 weeks gestation.

Sometimes, however, 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. Usually, the cyst is benign, painless, and goes away on its own. Corpus luteum cysts are considered "functional" cysts. This means they typically do not cause harm, rarely need medical intervention, and do not impact fertility.

Symptoms of Corpus Luteum Cysts

In many cases, people who have a corpus luteal cyst don't experience any discernable symptoms. In fact, a corpus luteal cyst will typically resolve on its own after a few menstrual cycles without the person even knowing it was there.

The most common symptom in those who do notice a corpus luteal cyst is a slight twinge of one-sided pain or mild tenderness during the menstrual cycle. This pain can mimic the type of pain associated with an ectopic pregnancy, so consult with a health care provider if you have any pain you are concerned about.

Large corpus luteum cysts have the potential to burst and cause internal bleeding. They can also lead to ovarian torsion, a rare but serious complication in which the ovary twists around surrounding tissues.

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 an external abdominal ultrasound.

While an ultrasound may be ordered if you have symptoms, cysts are often found during a routine ultrasound for other purposes, such as pregnancy confirmation or to investigate pelvic pain or unexplained vaginal bleeding.

There may be more opportunities to spot a corpus luteal cyst in pregnant people, simply because they're usually having routine ultrasound 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 for Corpus Luteum Cysts

Anyone with ovaries can get corpus luteum cysts, though they are more likely to develop in people taking medication to induce ovulation, like Clomid (clomiphene). These medications, which manipulate hormones to stimulate ovulation, are usually prescribed for people 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 luteal phase of the menstrual cycle, corpus luteum cysts can also develop when you are not pregnant. You can also develop one even if you aren't taking, or have never taken, medication to treat infertility.

In addition to ovulation-stimulating medications, the following put you at greater risk of developing a corpus luteum cyst:

• Endometriosis
• Hormonal imbalance
• Pelvic infection
• Pregnancy
• History of 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 can be more likely.

Treatment for Corpus Luteum Cysts

A corpus luteum cyst is usually not harmful, and they don't typically cause any complications during pregnancy, especially when they're discovered during the first trimester. If the cyst continues to grow or worsen, however, surgery may be recommended to reduce the risk of miscarriage.

If the cyst is causing pain, a health care provider may prescribe pelvic rest or pain medications. But in most cases, a corpus luteum cyst will resolve on its own without intervention.

Occasionally, a corpus luteum cyst will rupture. Pain may increase when this happens, but it tends to subside quickly. While rare, a corpus luteum cyst can cause the ovary to twist, which can be very painful and may require surgery to prevent further injury of the ovary.