Ovarian Cyst: Types, Symptoms, Treatment, Pregnancy and Fertility

An ovarian cyst is a fluid-filled sac on or inside an ovary. Most are functional cysts that form as part of the normal monthly cycle and disappear on their own within one to three periods, without any treatment. A smaller number, such as chocolate cysts (endometriomas), dermoid cysts and cystadenomas, do not go away by themselves and may need monitoring or keyhole surgery, especially if they cause pain or affect fertility. At Yaal Fertility Centre in Chennai, Dr. Rukkayal Fathima and our team see cysts on scan reports every week and help women understand which ones matter and which can simply be watched.

What Is an Ovarian Cyst?

Each month, several tiny fluid sacs called follicles start to grow in your ovaries. Usually one becomes dominant, releases an egg at ovulation, and then turns into a short-lived structure called the corpus luteum. All of this is normal, and on a scan these follicles look like small dark bubbles.

A cyst is a sac that is larger than a normal follicle, persists longer than expected, or is made of a different kind of tissue. Cysts range from under 3 cm to, rarely, more than 10 cm. They can affect one ovary or both.

The word "cyst" on a scan report often worries women, but the vast majority of ovarian cysts in women of reproductive age are benign (not cancer). What matters is the type of cyst, its size, how it looks on ultrasound, and whether it is causing symptoms.

Types of Ovarian Cyst at a Glance

Not all cysts behave the same way. This table sums up the common types and what each one usually means for you.

Functional Cysts: The Most Common Kind

Follicular and corpus luteum cysts make up most of the cysts found in women in their 20s and 30s. They are a by-product of ovulation, which is why they are so common in the reproductive years and rare after menopause. On ultrasound a simple functional cyst has a thin wall and clear fluid, with no solid parts.

A haemorrhagic cyst is a functional cyst that has bled into itself. It can cause sudden one-sided pain around mid-cycle or before a period. It looks more complex on a scan, with a lacy or net-like pattern inside, but it usually clears within a couple of cycles.

Chocolate Cyst (Endometrioma)

A chocolate cyst forms when endometriosis, tissue similar to the womb lining, grows inside the ovary. Each month it bleeds a little into the cyst, and the old blood turns thick and brown, hence the name. Endometriomas are often found in women with painful periods, pain during sex or difficulty conceiving.

Chocolate cysts are the type most closely tied to fertility, which is why we cover them in more detail below and in our guide to endometriosis and fertility.

Dermoid Cysts and Cystadenomas

A dermoid cyst grows from the cells that normally form eggs. Because these cells can make many kinds of tissue, a dermoid may contain fat, hair, skin or even tooth-like material. They are almost always benign and grow slowly. Their main risk is that a heavier ovary is more likely to twist.

A cystadenoma grows from the cells on the surface of the ovary. Serous ones contain watery fluid; mucinous ones contain thick, jelly-like fluid and can become quite large. Both are usually benign, but because they do not shrink on their own, they are normally removed once confirmed.

PCOS: Why Those "Cysts" Are Not True Cysts

Many women are told they have "cysts" when they have polycystic ovaries. In PCOS the ovary shows many small follicles, usually under 1 cm, lined up around the edge. These are eggs that started to grow and then paused because of the hormone pattern, not abnormal sacs that need removing.

So PCOS is managed by treating ovulation, weight, insulin and periods, not by draining follicles. Our guide to PCOS and fertility explains the condition in full. The two can exist together, though: a woman with PCOS can also have a separate functional cyst or endometrioma.

What Causes Ovarian Cysts?

The cause depends on the type of cyst.

• Ovulation itself. Functional cysts form when the normal cycle does not run perfectly: the follicle does not release its egg, or the sac left behind reseals and fills with fluid.
• Hormone treatment. Ovulation medicines and IVF stimulation make several follicles grow at once, so functional cysts are more common during and just after fertility treatment.
• Early pregnancy. The corpus luteum often stays larger in early pregnancy because it is making progesterone to support the baby.
• Endometriosis. Endometriosis tissue inside the ovary forms chocolate cysts.
• Growth of ovarian cells. Dermoids and cystadenomas come from the ovary's own cells growing in an unusual way. They are not caused by anything you did.
• Pelvic infection. Rarely, severe pelvic infection can form a pus-filled collection around the tube and ovary, which needs urgent treatment.

Ovarian cysts are not caused by eating certain foods, by lifting heavy things, or by stress alone. You may hear this from relatives, but it is not true.

Ovarian Cyst Symptoms

Many cysts cause no symptoms at all and are found on a routine scan, often during a pregnancy check or a fertility work-up. When there are symptoms, they usually come from the cyst pressing on nearby organs, bleeding a little, or making hormones.

Common Symptoms

• Dull ache or heaviness on one side of the lower tummy, which may come and go
• Pain during or after sex, especially with chocolate cysts sitting low in the pelvis
• Period changes, such as spotting, heavier flow or a late period
• Painful periods that are getting worse over time, which suggests endometriosis
• Bloating or a feeling of fullness, sometimes mistaken for gas or indigestion

Pressure Symptoms From Larger Cysts

A larger cyst takes up space in the pelvis and can cause:

• Passing urine more often, or feeling you cannot empty your bladder
• Constipation or pressure on the back passage
• A swollen lower tummy, or clothes feeling tight at the waist
• Lower back ache
• Feeling full quickly when eating

None of these symptoms is specific to cysts. Fibroids, a bulky uterus, urinary infections and bowel problems can feel similar, which is why an ultrasound is the way to find out.

When to Worry: Ovarian Torsion and Cyst Rupture

Most cysts stay quiet. Two complications, however, need same-day medical care.

Ovarian Torsion: A Twisted Ovary

A cyst can make the ovary heavier, and a heavier ovary can twist on the stalk that carries its blood supply. This is called ovarian torsion. It cuts off blood flow, and without prompt surgery the ovary can be lost. Torsion is more likely with cysts of about 5 cm or more, with dermoid cysts, and during pregnancy or IVF stimulation, when the ovaries are enlarged.

Cyst Rupture

A cyst can burst. Small functional cysts often rupture quietly and the fluid is reabsorbed with only a day or two of soreness. A larger or bleeding cyst can cause sudden severe pain, and occasionally enough internal bleeding to need surgery.

Emergency Warning Signs

Go to the nearest emergency department straight away if you have:

• Sudden, severe pain in the lower tummy or pelvis, especially on one side
• Pain with nausea or vomiting
• Fainting, dizziness, a racing heart or feeling cold and clammy
• Fever with tummy pain
• Pain in the shoulder tip together with tummy pain, which can mean internal bleeding
• Severe pain in early pregnancy, which also needs an urgent scan to rule out an ectopic pregnancy

Do not wait for your next clinic appointment if any of these happen. Time matters for saving the ovary.

How an Ovarian Cyst Is Diagnosed and Followed Up

Ultrasound Is the Main Test

A transvaginal ultrasound, where a slim probe is placed in the vagina, gives the clearest view of the ovaries. If an internal scan is not suitable, for example in unmarried women or young girls, a tummy (transabdominal) scan can be used. Our ultrasound services team looks at:

• Size of the cyst in centimetres
• Wall: thin and smooth, or thick and uneven
• Contents: clear fluid, blood, ground-glass fluid (typical of chocolate cysts), fat or solid areas
• Partitions (septa) inside the cyst
• Blood flow within any solid part, checked with Doppler

Most cysts can be identified by type from the ultrasound alone. Many scan reports now use a standard scoring system that sorts cysts into low, intermediate or higher concern, which helps your doctor decide what to do next.

Phrases You May See on a Scan Report

Repeat Scans and Other Tests

For a simple-looking cyst in a woman with no worrying symptoms, the usual plan is a repeat scan after one to three cycles, ideally just after a period, when functional cysts are least likely to be present. If it has gone, no further action is needed.

If a cyst looks complex, keeps growing or does not go away, your doctor may suggest:

• Blood tests such as CA-125. This marker is often raised in benign conditions like endometriosis, periods and pregnancy, so it is read alongside the scan, never on its own.
• MRI of the pelvis, when ultrasound cannot clearly tell what a cyst is made of.
• AMH blood test, to measure egg reserve before any surgery on the ovary. Our article on the AMH test explains what the numbers mean.

Ovarian Cyst Treatment: Watchful Waiting or Surgery?

Treatment depends on the type and size of the cyst, your symptoms, your age and whether you plan to have children.

When Watchful Waiting Is Right

Watching with repeat scans is the right choice for most cysts in women of reproductive age. It is suitable when the cyst:

• Looks simple or clearly haemorrhagic on ultrasound
• Is small to moderate in size
• Is not causing significant pain
• Has no features that need further checking

Waiting avoids unnecessary surgery on an ovary that will heal itself. Birth control pills are sometimes used to stop new functional cysts forming in women who get them repeatedly, but they do not shrink a cyst that is already there.

When Surgery Is Recommended

Surgery is usually advised when a cyst:

• Has not gone away after a few months of follow-up
• Is large, often around 5 cm or more depending on the type
• Is a dermoid or cystadenoma, which will not resolve by itself
• Causes ongoing pain or pressure
• Has twisted or ruptured and is bleeding
• Has features that need a tissue diagnosis

Keyhole Surgery That Protects the Ovary

Most benign cysts are removed by laparoscopy (keyhole surgery) through small cuts in the tummy. The aim in a woman who wants children is a cystectomy: peeling out the cyst wall and leaving healthy ovarian tissue behind, rather than removing the whole ovary. Our laparoscopic surgery service and our article on laparoscopy for fertility cover what to expect, from admission to recovery.

Protecting Your Ovarian Reserve

Every ovary has a limited supply of eggs. Surgery on the ovary, especially for chocolate cysts, can remove or damage some healthy tissue along with the cyst wall, and AMH levels often fall after it. This is why:

• We check AMH and the antral follicle count before planning surgery
• We avoid operating on the ovary more than once when possible
• Repeat surgery for recurrent chocolate cysts is weighed carefully against going straight to fertility treatment
• For some women with low reserve, egg or embryo freezing before surgery is discussed

If your reserve is already low, our guide to low ovarian reserve treatment options explains what can and cannot help.

Can an Ovarian Cyst Cause Infertility?

For most women, no. Functional cysts come and go with ovulation and do not harm fertility. In fact, a corpus luteum cyst is a sign that you ovulated. Women with one ovary affected by a cyst usually still ovulate from the other.

Some cyst types and their causes can affect fertility, though.

Chocolate Cysts and Endometriosis

Endometriomas are the cysts most clearly linked to difficulty conceiving. The reasons are mostly the underlying endometriosis rather than the cyst itself:

• Inflammation in the pelvis can affect egg quality and the way sperm and egg meet
• Endometriosis can cause adhesions (scar tissue) that bind the tubes and ovary together
• The cyst can slowly reduce healthy ovarian tissue around it
• Surgery to remove it can lower egg reserve further

The decision between surgery and going straight to fertility treatment is individual. Our endometriosis and fertility guide goes through how stage, age and reserve shape that choice.

Large Cysts and Repeated Surgery

Very large dermoids or cystadenomas can distort the pelvis, and repeated operations on the same ovary can reduce its egg supply over time. Careful, ovary-sparing surgery done once, by a surgeon who understands fertility, keeps that loss to a minimum.

When the Real Issue Is Ovulation

When the "cysts" are PCOS follicles, the fertility problem is irregular or absent ovulation, which is very treatable. Tracking your cycle with a follicular study shows whether and when you ovulate, and helps time treatment.

Ovarian Cyst and Pregnancy

Cysts Found in Early Pregnancy

Finding a cyst on an early pregnancy scan is common and usually reassuring. The corpus luteum often appears as a cyst in the first trimester. It produces progesterone that supports the pregnancy until the placenta takes over, and it fades away on its own, usually by the second trimester.

Cysts That Persist in Pregnancy

Dermoid cysts, chocolate cysts and cystadenomas that were present before pregnancy may remain. Most are simply watched with scans during antenatal care. If a cyst grows quickly or causes pain, surgery is usually timed for the second trimester when it is safest. Torsion or rupture in pregnancy is treated as an emergency at any stage.

Planning Pregnancy With a Known Cyst

If you know you have a cyst and are planning to conceive, it is worth seeing a gynaecologist first. A small simple cyst rarely needs anything. A larger dermoid or cystadenoma is often best removed before pregnancy, so you avoid the risk of it twisting while you are pregnant.

Ovarian Cysts and IVF

Cysts on the Baseline Scan

Before IVF stimulation starts, a baseline scan checks that the ovaries are quiet. If a functional cyst is found, especially one making hormones, your team may wait a cycle, use medicines to settle it, or drain it before starting. This helps the follicles grow evenly and avoids a poor or confusing response.

Endometriomas and Egg Collection

Many women with chocolate cysts go through IVF without removing them first. During egg collection, the specialist plans the needle path to avoid the cyst, because puncturing it carries a small risk of infection. Surgery before IVF is considered mainly when cysts are very large, block access to the follicles, cause severe pain, or need a diagnosis.

Cysts After Stimulation

IVF and ovulation medicines enlarge the ovaries, and small functional cysts are common afterwards. Most settle on their own over the next cycle or two. Your team will recheck with a scan before any frozen embryo transfer.