Functional Ovarian Cysts: When to Watch, When to Act
Key Takeaways
A functional ovarian cyst is a fluid-filled sac linked to the normal cycle. Most go away on their own within a few weeks or months. Sudden severe pelvic pain needs urgent care; a cyst that persists or looks complex needs further checks.
Key evidence: ACOG patient information on ovarian cysts Cochrane review of oral contraceptives for functional ovarian cysts RCOG guidance on simple cysts before menopause
What a functional ovarian cyst is
A functional cyst forms during the normal cycle, around the time an egg is released (ovulation). It is often found by chance on a scan. The name means it is linked to the cycle. Other growths, such as endometriomas or dermoid cysts, have different causes (ACOG patient information).
Two common types:
| Type | How it forms |
|---|---|
| Follicular | The follicle, a small sac that holds an egg, does not release it and keeps filling with fluid. |
| Corpus luteum | After the egg is released, the structure left behind fills with fluid or blood. |
Being linked to the cycle does not make a cyst harmless in every situation. Symptoms and the scan decide whether it needs care.
Symptoms — often none
Many functional cysts cause no symptoms. Possible symptoms include:
- one-sided pelvic pain or pressure,
- bloating,
- temporary menstrual irregularity,
- pain with intercourse in some cases.
Sudden severe pelvic pain needs urgent assessment. A cyst may have burst, or the ovary may have twisted (torsion). Vomiting, dizziness, or faintness with the pain also call for urgent care. Do not wait for the next planned scan.
How ultrasound sorts them
A scan through the vagina (transvaginal ultrasound) is the main test for a mass in or near the ovary, according to RCOG guidance. A simple cyst has a thin wall and fluid inside. A cyst that contains blood can look more complex and still be benign, meaning non-cancerous (SRU ultrasound consensus).
Interpretation depends on:
- age,
- symptoms,
- size,
- whether the picture changes on follow-up,
- and features that raise concern for another diagnosis.
CA-125 is a blood test sometimes used to assess an ovarian mass. It is not needed for every clearly simple cyst before menopause. A result has to be read alongside the scan and symptoms (RCOG guidance).
Treatment options
Observation
Many functional cysts go away within six to eight weeks (ACOG patient information). The need for another scan depends on the type, size, and symptoms.
Before menopause, simple cysts under 50 mm (5 cm) generally need no follow-up if there are no symptoms (2011 RCOG guideline). They usually resolve within about three menstrual cycles. This advice does not cover a painful cyst or one that has an unclear scan appearance.
Pain control
For mild pain, a clinician may suggest a painkiller and changes to activities that cause discomfort. New or worsening pain needs a fresh assessment.
Hormonal suppression
Combined contraceptive pills do not make an existing functional cyst go away faster (Cochrane review of contraceptive pills). They may be prescribed for birth control or another reason, which is a separate decision.
Surgery
Surgery may be considered for a very large or suspicious cyst, or for twisting of the ovary or heavy bleeding. A cyst that persists also needs reassessment: it may not be functional (RCOG guidance). If surgery is needed, preserving ovarian tissue matters for future fertility.
Fertility and IVF cycles
A functional cyst on its own does not explain why pregnancy has not happened. Its type matters. An endometrioma, which is linked to endometriosis, needs a different assessment from a functional cyst. Polycystic ovary syndrome (PCOS) is also a separate diagnosis, based on more than a cyst on a scan (Pasquali and Gambineri’s diagnostic review).
Before ovarian stimulation for IVF or egg freezing, a scan may show a cyst left from the previous cycle. The scan and any symptoms help decide what to do next. The approach below describes the factors I use in that decision. For the separate question of PCOS, see the PCOS guide.
Dr. Aksoy’s approach to a cyst on the baseline scan
I first distinguish a small, simple residual functional cyst from an endometrioma or another lesion. When the patient has no pain, basal estradiol is suppressed, and the cyst will not interfere with follicle counting or access during oocyte retrieval, stimulation can often begin with monitoring.
Further assessment — and often postponement — is more appropriate when the cyst is hormonally active, raises estradiol, disrupts follicular synchrony, is large enough to obstruct retrieval, or has septa, solid areas, or papillary projections.
Aspiration means draining the cyst with a needle. I do not use it routinely. I discuss it in selected cases where a persistent, large simple cyst blocks access to the eggs. I do not aspirate an endometrioma merely because it occupies space. Drainage needs anaesthesia and carries a risk of procedural complications (Cochrane review), and a simple cyst often fills up again afterwards (RCOG guidance).
Research has not established whether drainage improves IVF results. The Cochrane review of cyst drainage found too little evidence to tell whether it changes pregnancy rates or the number of eggs collected. None of the studies reported live births (a baby born alive, which is a different outcome from a pregnancy seen on a scan) or complication rates.
Evidence box: cyst drainage before IVF
The 2014 review included three trials with 339 women. Participants were assigned by chance to drainage or no drainage (randomised trials). The cysts were simple, functional, and over 20 mm; all trials used agonist stimulation protocols. The evidence was rated low quality. These studies cannot settle the benefit or safety of routine drainage in current IVF practice.
Frequently Asked Questions for Dr. Aksoy
Why do functional ovarian cysts form?
Most form during a normal cycle. Each month a follicle usually grows, ruptures, and releases an egg. Sometimes the follicle does not rupture and keeps filling with fluid, forming a follicular cyst. A cyst can also form after ovulation, when the leftover corpus luteum fills with fluid or blood.
These cysts are common in women of reproductive age, and most disappear on their own within a few weeks or a few cycles. A cyst does not mean the ovary is diseased, and on its own it does not show that ovarian reserve has fallen. Not every cyst needs surgery or medication.
Combined contraceptive pills may reduce new functional cysts by suppressing ovulation. They have not been shown to make an existing cyst disappear faster, so I do not prescribe them simply to shrink one. What matters to me is the ultrasound appearance, the size, the patient’s age, and her symptoms.
What does a functional cyst look like on ultrasound?
I mainly use transvaginal ultrasound. Simple follicular cysts usually look round or oval, with a thin wall and fluid content that appears black. They do not all look the same. A corpus luteum cyst may have a thicker wall, and bleeding inside may show fine net-like lines or clots. This can worry a patient, but on its own it does not mean the cyst is malignant.
What matters most is the internal structure and the wall, not only the size. If I see solid areas, irregular thickening, or suspicious blood vessels, I do not treat it as a simple functional cyst and may investigate further.
Most functional cysts with bleeding shrink or disappear within about six to eight weeks, so a repeat scan can clarify the picture. Small, typical simple cysts do not all need repeated scans. A cyst on the scan is not in itself a cause for concern. How it looks and how it changes over time is what counts.
Does a functional cyst prevent pregnancy?
Usually not. Many women with a functional cyst can conceive naturally. The type matters. If a follicle grows but does not rupture, ovulation may not happen that cycle, which may lower the chance for that month. That does not mean she cannot ovulate later or is infertile.
A corpus luteum cyst forms after ovulation and produces progesterone, which supports early pregnancy. Seeing one on an early pregnancy scan is often normal. A study of women scanned in early pregnancy found that most cysts detected were physiological and resolved (Condous et al. 2004).
I do not advise a woman trying to conceive to postpone her treatment straight away because of a functional cyst. First I look at its size, appearance, and pain, and whether it affects ovulation. Before IVF, I also check whether the cyst is producing hormones. Some cysts may delay the start of treatment; others can simply be followed.
Especially when a woman is older or her ovarian reserve is reduced, I do not want to lose time unnecessarily over a small cyst that looks harmless. With a very large or painful cyst, the approach may change. Sudden severe lower abdominal pain, nausea, or fainting needs urgent assessment for torsion or bleeding.
What matters to me is not the cyst itself, but whether it really affects ovulation and the fertility treatment we are planning.
Sources
- American College of Obstetricians and Gynecologists. Ovarian Cysts.
- Royal College of Obstetricians and Gynaecologists. Management of Suspected Ovarian Masses in Premenopausal Women. Green-top Guideline No. 62. 2011.
- Grimes DA, Jones LB, Lopez LM, Schulz KF. Oral contraceptives for functional ovarian cysts. Cochrane Database of Systematic Reviews. 2014;(4):CD006134. doi:10.1002/14651858.CD006134.pub5.
- McDonnell R, Marjoribanks J, Hart RJ. Ovarian cyst aspiration prior to in vitro fertilization treatment for subfertility. Cochrane Database of Systematic Reviews. 2014;12:CD005999. doi:10.1002/14651858.CD005999.pub2.
- Condous G, Khalid A, Okaro E, Bourne T. Should we be examining the ovaries in pregnancy? Prevalence and natural history of adnexal pathology detected at first-trimester sonography. Ultrasound Obstet Gynecol. 2004;24(1):62-66. doi:10.1002/uog.1083. PMID 15229918.
- Pasquali R, Gambineri A. A comprehensive approach in diagnosing the polycystic ovary syndrome. Womens Health (Lond). 2015;11(4):501-512. doi:10.2217/whe.15.13. PMID 25756387.
- Levine D, Brown DL, Andreotti RF, et al. Management of Asymptomatic Ovarian and Other Adnexal Cysts Imaged at US: Society of Radiologists in Ultrasound Consensus Conference Statement. Radiology. 2010;256(3):943–954. doi:10.1148/radiol.10100213.
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The content has been created by Dr. Senai Aksoy and medically approved.