Having one or two small cysts on your ovaries at any given time is completely normal and expected. In fact, your ovaries produce fluid-filled sacs every single menstrual cycle as part of how eggs develop, so finding cysts on an ultrasound rarely means something is wrong. A large screening study of nearly 40,000 women found that about 15% of premenopausal women and 8% of postmenopausal women had visible ovarian cysts at the time of their scan, most of which were harmless.
Why Your Ovaries Make Cysts Every Month
Each menstrual cycle, your brain signals your ovaries to start developing eggs. Between 11 and 20 tiny fluid-filled sacs (called follicles) begin growing in response, each one housing an immature egg. These follicles measure roughly 2 to 9 millimeters across and are visible on ultrasound. If you had a scan during this phase, you’d see a cluster of small round structures on each ovary, and all of them are normal.
As the cycle progresses, one follicle outpaces the rest and becomes the “dominant” follicle. It releases increasing amounts of estrogen, which signals your brain to dial back the hormone that was fueling all the other follicles. Those smaller follicles gradually shrink and get reabsorbed. The dominant one continues growing until it ruptures and releases an egg at ovulation.
After ovulation, the ruptured follicle transforms into a temporary structure that produces hormones to support a potential pregnancy. This structure can fill with fluid or blood, forming what’s called a corpus luteum cyst. It typically dissolves on its own within a couple of weeks if pregnancy doesn’t occur. So at various points in your cycle, having anywhere from a handful to over a dozen small follicles, plus one or two functional cysts, is entirely routine.
What Counts as a Normal Number
A healthy ovary in a reproductive-age woman typically shows between 14 and 35 small follicles total across both ovaries on ultrasound. This number naturally declines with age. These aren’t considered “cysts” in the medical sense, even though they look like small round spots on a scan. They’re simply part of your ovarian reserve, the pool of eggs your body draws from each cycle.
The distinction matters because the word “cyst” on an ultrasound report can sound alarming when it’s really just describing normal anatomy. A functional cyst, one that forms during ovulation or just after, is also normal. Most women will develop at least one or two of these per year without ever knowing it, because they cause no symptoms and resolve without treatment.
When the Number Becomes a Concern
The threshold where follicle count raises a red flag is 20 or more follicles on a single ovary. Under the latest international guidelines, this pattern, combined with other signs like irregular periods or elevated androgens, can point toward polycystic ovary syndrome (PCOS). The key word is “combined.” Having a high follicle count alone doesn’t automatically mean PCOS. The diagnosis requires at least two of three criteria: excess follicles or enlarged ovaries, irregular or absent periods, and signs of elevated male hormones like acne or excess hair growth.
Ovarian volume also plays a role. An ovary measuring 10 milliliters or more in volume is considered enlarged and factors into the same diagnostic picture. If your ultrasound shows a high follicle count but your periods are regular and you have no other symptoms, your ovaries may simply be on the higher end of normal.
Size Matters More Than Number
For simple cysts (the kind that are smooth, fluid-filled, and have thin walls), size is a better indicator of concern than how many you have. In reproductive-age women, simple cysts smaller than 5 centimeters generally don’t even need follow-up imaging. They’re expected to resolve on their own within one to three menstrual cycles.
Simple cysts up to 10 centimeters can still be benign and are often monitored with repeat ultrasound rather than surgically removed. The American College of Obstetricians and Gynecologists considers these likely harmless when they have straightforward features on imaging. Beyond 10 centimeters, or when a cyst has irregular walls, solid areas, or multiple internal compartments, further evaluation is typically warranted.
What makes a cyst “simple” on ultrasound is specific: it’s a single fluid-filled pocket with smooth inner walls and no solid tissue inside. If your report describes something with thick walls, internal projections, or mixed solid and fluid components, that’s a different category and gets evaluated more carefully.
Cysts After Menopause
Ovarian cysts don’t stop appearing after menopause, though they become less common. Studies estimate that between 5% and 17% of postmenopausal women have ovarian cysts at any given time, and one large cancer screening trial found simple cysts in 14% of women over 55.
After menopause, the guidelines are slightly more conservative. Simple cysts 3 centimeters or smaller on one ovary are considered clinically insignificant, according to the Royal College of Obstetricians and Gynaecologists. They don’t require follow-up. Cysts between 3 and 5 centimeters may be monitored with a repeat ultrasound in four to six months. Larger cysts or those with any unusual features get a more thorough workup, but even in postmenopausal women, simple cysts up to 10 centimeters can be safely watched rather than immediately removed.
What Your Ultrasound Report Actually Means
If you’ve had a pelvic ultrasound and the report mentions cysts, the first thing to look at is how they’re described. “Simple cyst” or “follicle” in a premenopausal woman is almost always normal physiology. Multiple small follicles are expected. Even a single larger cyst under 5 centimeters is typically a functional cyst that will go away on its own.
The features that genuinely warrant attention are solid components inside the cyst, irregular or thick walls, multiple internal dividers, or the presence of fluid in the abdomen that shouldn’t be there. These characteristics shift a finding from “normal variant” to “needs closer evaluation.” The number of cysts on your ovaries is far less important than what those cysts look like and whether they’re causing symptoms like persistent pelvic pain, bloating, or pressure.
For most women, finding cysts on an ultrasound is like finding that your heart beats: it’s what the organ is supposed to do. Your ovaries are cyst-making machines by design, and the vast majority of what shows up on a scan is simply evidence that they’re working.