An ultrasound report that says “bilateral polycystic ovaries” or “bilateral PCOM” can look alarming. Many women read it as a diagnosis, or worry that their ovaries are full of cysts that need removing. Neither is true.
A scan shows how your ovaries look on one day. Whether you have polycystic ovary syndrome (PCOS), now also called polyendocrine metabolic ovarian syndrome (PMOS), also depends on your periods, signs of excess male-type hormones and blood tests. Our PCOS hub on symptoms, tests and treatment covers the full condition.
What “bilateral polycystic ovaries” means on your ultrasound report
“Bilateral” simply means both ovaries. “Polycystic ovarian morphology” (PCOM) means the ovaries have more small follicles than usual, or are larger than usual. The “cysts” are follicles: small fluid-filled sacs, each holding an immature egg. They are not the kind of cyst that needs an operation.
Here is what each common phrase means, with the thresholds from the 2023 international PCOS guideline, which the hub follows.
| Phrase on the report | What it means | 2023 guideline threshold or note |
|---|---|---|
| Bilateral | Both ovaries show the same appearance | Only one ovary needs to meet the threshold to count as PCOM; “bilateral” does not make it a diagnosis |
| Polycystic ovarian morphology (PCOM), polycystic ovaries, “PCO pattern” | A description of what the ovaries look like | One of three possible features of PCOS; on its own, not PCOS |
| Follicle number per ovary (FNPO), “multiple follicles” | The number of 2–9 mm follicles counted through the whole ovary | 20 or more in at least one ovary, on a transvaginal scan with a modern probe; older reports may use the 2003 cut-off of 12 |
| Follicles per section (FNPS) | Follicles seen in one slice of the ovary | 10 or more in at least one ovary, used with older machines or an abdominal scan |
| Ovarian volume (in mL, cc or cm³; all the same unit) | The size of each ovary | 10 mL or more in at least one ovary, used when follicles cannot be counted accurately, and the main measure on an abdominal scan |
| Peripheral follicles, “string of pearls” | Small follicles lined up around the edge of the ovary | A common picture in polycystic ovaries, but not part of the diagnostic criteria |
| Dominant follicle, corpus luteum, “simple cyst” | A follicle of 10 mm or more, or the structure left after ovulation; both are normal parts of a cycle | Not counted in ovarian volume; the other ovary’s count is used instead |
| Endometrial thickness (ET) | The thickness of the womb lining, in mm | The guideline asks scan reports to include it. Normal varies through the cycle; an excessively thick lining needs a doctor’s review |
One ovary is enough to meet the definition of PCOM, so “bilateral” describes the scan; it does not tell you whether you have PCOS. The 2003 international consensus definition also said a single polycystic ovary is sufficient and that follicle arrangement is not needed.
The 20-follicle threshold assumes a transvaginal probe that can see every follicle; transabdominal scans should mainly report volume or follicles per section. The Federation of Obstetric and Gynaecological Societies of India (FOGSI) uses the same thresholds in its 2024 recommendations, for probes that include 8 MHz, so Indian and international advice agree here.
For the lining, a radiology reference gives typical values of 2–4 mm during a period, up to 11 mm before ovulation and 7–16 mm after it, as a guide only. Let your doctor judge the number.
Polycystic ovaries on a scan are not the same as PCOS
PCOS is diagnosed when at least two of three features are present, after other causes are ruled out: irregular or absent ovulation, signs of androgen excess (on the skin or in blood tests), and PCOM on ultrasound or a raised anti-Müllerian hormone (AMH) level. A scan alone can supply at most one of the three. The hub’s diagnosis and tests section explains the rest.
Polycystic-looking ovaries are common in women with no syndrome at all:
- A US study of 262 women aged 25–45 who ovulated normally found that 32% met the older 12-follicle definition. The finding became less common with age, and these women did not have the metabolic problems seen in PCOS.
- An Androgen Excess and PCOS Society task force (2014) noted PCOM in as many as 30% of young women.
- A small study followed 23 women with regular cycles and PCOM for about eight years on average. Only one developed irregular periods suggesting PCOS, and 11 no longer had PCOM.
These studies used older, lower thresholds, so fewer women would qualify today. The message holds: the 2003 consensus said a woman with polycystic ovaries but no ovulation problem or androgen excess should not be considered to have PCOS.
If you already have both irregular cycles and signs of androgen excess, the guideline says an ovarian ultrasound is not necessary for diagnosis.
Why scans are not used for diagnosis in teenagers
The international guideline’s recommendations for adolescents say pelvic ultrasound and AMH are not recommended for PCOS diagnosis until 8 years after the first period, because ovaries naturally have many follicles during the teenage years. FOGSI says the same: no ultrasound for diagnosis before a gynaecological age of 8 years. The National Health Service (NHS) in the UK only does the scan for people over 18. A teenager’s periods and symptoms matter, not the scan picture.
AMH: the blood test that can replace the scan in adults
Since 2023, the guideline says serum AMH could be used instead of ultrasound to define PCOM in adults. AMH is a hormone made by small follicles, so more follicles usually means a higher level. It is a convenient option if a transvaginal scan is not acceptable to you.
The guideline sets clear limits:
- AMH should not be used as a single test for PCOS.
- It should not yet be used in adolescents.
- Either AMH or ultrasound may be used, but not both, to limit over-diagnosis.
- Levels vary with age (they peak around 20–25), are lower at higher body mass index (BMI), may be suppressed by the combined pill, and may vary across the cycle.
- Laboratories should use cut-offs specific to their test kit, so do not compare one lab’s result with another lab’s range.
If you already have a scan showing PCOM, an AMH test on top of it usually adds nothing to the diagnosis.
Is bilateral polycystic ovaries dangerous on its own?
Polycystic-looking ovaries on their own are not known to be dangerous. The 2014 task force concluded that PCOM is not associated with significant health consequences without other PCOS features, though inconsistent definitions mean this cannot be said with absolute certainty. The US study above found no metabolic differences, and said isolated polycystic ovaries are not by themselves a reason for metabolic testing.
The same task force described one clear exception: fertility treatment with hormone injections, such as in-vitro fertilisation (IVF). Ovaries with many follicles can respond very strongly, raising the risk of ovarian hyperstimulation syndrome (OHSS). If you ever have fertility treatment, tell the specialist about this scan.
What matters is whether the full PCOS criteria are met. If they are, the long-term risks on the hub, such as diabetes and a thickened womb lining after long gaps between periods, come from the syndrome, not from how the ovaries look. See the difference between polycystic ovary disease (PCOD) and PCOS for why reports use two labels, and irregular periods and when to worry for why long gaps matter.
Follow-up depends on your symptoms, not the picture. In our view, if your periods are regular and you have no excess hair, acne or other symptoms, polycystic ovaries found on a scan done for another reason do not need repeat scans. If you have irregular periods, unwanted hair or difficulty conceiving, see a doctor; our guide to PCOS symptoms, including skin changes and acne lists what to look for.
PCOS ultrasound: transabdominal or transvaginal, and when in your cycle
The guideline calls the transvaginal scan the most accurate way to look for PCOM, but only if it is acceptable to you. FOGSI prefers it if you are sexually active and comfortable with it.
| Scan type | How it is done | What it can reliably report | Good to know |
|---|---|---|---|
| Transabdominal | A probe moved over the lower tummy, usually with a full bladder | Ovarian volume, and follicles in one section | The usual choice if you have never been sexually active or prefer not to have an internal scan; images can be less clear at a higher weight |
| Transvaginal | A thin probe placed gently inside the vagina, with an empty bladder | A full follicle count per ovary, ovarian volume and the womb lining | The most accurate for PCOM; you can ask for a female sonographer or a chaperone, and you can ask to stop at any time |
Timing also affects the result. A review of ultrasound criteria describes the standard approach:
- If your periods are regular, the scan is best done early in the cycle, in the first few days after a period starts.
- If your periods are very irregular or absent, it can be done on any day, or a few days after a bleed brought on by a doctor-prescribed hormone.
- If a dominant follicle (larger than 10 mm) or a cyst is seen, the assessment is repeated in a later cycle.
Tell the sonographer the date of your last period; the guideline says every report should include it. Mention if you have recently taken the pill, which the task force said is best avoided before assessing PCOM. Do not stop a prescribed pill for a scan without asking your doctor.
What to ask your doctor, and why a report alone should not lead to medicines
Take the report, your period dates for the last few months and a list of symptoms to a doctor, usually a gynaecologist. Useful questions:
- Do I meet the criteria for PCOS, or is this only how my ovaries look?
- Which threshold was used: a full follicle count, follicles per section, or volume? Was it a transvaginal or abdominal scan?
- Was the scan done at the right time in my cycle, and is my lining thickness normal for that time?
- Do I need blood tests to rule out thyroid, prolactin or other causes, or to check androgens?
- If it is not PCOS, do I need any follow-up at all?
No medicine treats how the ovaries look on a scan. PCOS treatment is aimed at symptoms and risks, such as irregular periods, excess hair, acne, difficulty conceiving or blood sugar, and depends on your goals. A report alone is not a reason to start hormone tablets, “cyst” treatment or a supplement, whether suggested by a lab, a chemist or a website. Healthy eating, activity and sleep support your health either way, but they will not change what a scan shows and cannot replace a doctor’s assessment.
When to see a doctor
The hub has the full list of PCOS warning signs.
Emergency: get help now (call 112)
- Sudden, severe pelvic pain, or tummy pain with feeling sick or vomiting. NHS advises urgent help for these signs, which can mean an ovarian cyst has twisted or burst.
- Heavy bleeding that soaks through a pad soon after you put it on, or bleeding with dizziness or fainting.
- If you could be pregnant: severe or one-sided lower tummy pain, shoulder-tip pain, fainting or heavy bleeding.
Prompt review: within days to a few weeks
- No period for three months or more when you are not pregnant.
- Bleeding between periods or spotting you did not expect; FOGSI advises checking the womb lining with a transvaginal scan in women with PCOS who have unexpected bleeding.
- A report that mentions a cyst other than small follicles, or a thick womb lining.
- Excess hair or acne that worsens quickly over a few months, or a deepening voice.
Routine review
Book an appointment if you have irregular periods, unwanted facial or body hair, persistent acne, or have been trying to conceive without success, or if you simply want the report explained.
How Disha can help
Disha is an AI health coach that chats and calls in Hindi, English and Hinglish. It does not replace a doctor, and it does not diagnose, read scan reports, prescribe or provide emergency care. It helps with the daily habits your doctor recommends: meals, movement, sleep and stress. Its onboarding call of about 15–20 minutes is conducted by Disha, the AI; no human doctor is on the call. Read how Disha coaching works.
This is not medical advice. This page is general education for adults (18+), not a diagnosis or treatment plan, and it cannot interpret your own report. Do not start, stop or change any medicine, including the pill, because of a scan result. If you are pregnant, breastfeeding or having fertility treatment, ask your specialist how this applies to you. In an emergency, call 112.
Frequently asked questions
What does bilateral polycystic ovaries mean?
It means both ovaries have more small follicles than usual, or are larger than usual, on an ultrasound. The 2023 international guideline counts 20 or more follicles, or a volume of 10 mL or more, in at least one ovary. The “cysts” are normal immature egg sacs, not growths. It describes a scan picture and is not, by itself, a diagnosis of PCOS.
Is a bilateral polycystic ovary the same as PCOS?
No. PCOS needs at least two of three features: irregular ovulation, signs of androgen excess, and polycystic ovaries or a raised AMH, after other causes are excluded. Polycystic ovaries alone count as one feature. Studies using older thresholds found polycystic-looking ovaries in about 30% of young women, most of whom do not have the syndrome.
What is bilateral polycystic ovarian morphology?
“Polycystic ovarian morphology” (PCOM) is the technical name for polycystic-looking ovaries, and “bilateral” means both sides. On a modern transvaginal scan, the guideline threshold is 20 or more follicles of 2–9 mm in an ovary. On an abdominal scan or older machine, an ovarian volume of 10 mL or more, or 10 or more follicles in one section, is used instead.
Can I get pregnant with bilateral polycystic ovaries?
If your periods are regular and you have no other PCOS features, polycystic-looking ovaries alone have not been shown to delay pregnancy, according to studies reviewed by the Androgen Excess and PCOS Society task force. If you have irregular periods or have been trying for a while without success, see a doctor. If you ever have fertility injections, tell the specialist about the scan, because the ovaries may respond strongly.
Can polycystic ovaries go back to normal?
They can. In one small study of women with regular cycles, 11 of 23 with polycystic-looking ovaries no longer met the definition when scanned again years later. Follicle numbers naturally fall with age. This does not mean any diet or supplement “dissolves cysts”; there is nothing to dissolve. What matters is your symptoms, not the picture.
Is a transvaginal scan necessary for PCOS?
No. The guideline calls it the most accurate way to see PCOM, but only if it is acceptable to you. An abdominal scan can measure ovarian volume instead, and in adults an AMH blood test can replace the scan altogether. If you already have irregular periods and signs of androgen excess, no scan or AMH test is needed to diagnose PCOS.
My teenage daughter’s scan says polycystic ovaries. Does she have PCOS?
Not because of the scan. The international guideline and FOGSI do not recommend ultrasound for diagnosing PCOS until 8 years after the first period, because many follicles are normal in teenage ovaries. In adolescents, diagnosis needs both irregular periods and signs of androgen excess. Take her to a doctor if her periods are very irregular or she has marked hair growth or severe acne.
Sources
- Teede HJ, Tay CT, Laven JJE, Dokras A, Moran LJ, Piltonen TT, Costello MF, Boivin J, Redman LM, Boyle JA, Norman RJ, Mousa A, Joham AE. Recommendations From the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. Journal of Clinical Endocrinology and Metabolism, 2023. Supports: diagnostic criteria; FNPO of 20 or more, and ovarian volume of 10 mL or more or FNPS of 10 or more, in at least one ovary; transvaginal approach most accurate if acceptable; transabdominal scans reporting volume or FNPS; no scan needed with irregular cycles and androgen excess; reporting items including last period, dominant follicles and endometrial thickness; AMH as an alternative in adults, not a single test, not in adolescents, not both tests, influencing factors and kit-specific cut-offs; biopsy and withdrawal bleed considered for excessive endometrial thickness.
- Peña AS, Witchel SF, Boivin J, Burgert TS, Ee C, Hoeger KM, Lujan ME, Mousa A, Oberfield S, Tay CT, Teede H. International evidence-based recommendations for polycystic ovary syndrome in adolescents. BMC Medicine, 2025. Supports: pelvic ultrasound and AMH not recommended for PCOS diagnosis until 8 years after the first period; rapid increase in follicles during adolescence.
- Federation of Obstetric and Gynaecological Societies of India (FOGSI) and ICOG. Good Clinical Practice Recommendations: Update in Managing PCOS in Women. 2024. Supports: ultrasound only in adults and not before a gynaecological age of 8 years; transvaginal approach preferred if sexually active and acceptable; FNPO of 20 or more and/or volume of 10 mL or more with probes including 8 MHz; endometrial thickness assessed by transvaginal scan with unexpected bleeding.
- NHS. Polyendocrine metabolic ovarian syndrome (PMOS) and Ovarian cyst. Current patient guidance. Supports: PMOS as the new name for PCOS; ultrasound only done in people over 18; most functional cysts are harmless and go away in a few months; urgent help for sudden severe pelvic pain, or tummy pain with nausea or vomiting.
- Balen AH, Laven JSE, Tan SL, Dewailly D. Ultrasound assessment of the polycystic ovary: international consensus definitions. Human Reproduction Update, 2003. Supports: the older threshold of 12 follicles; a single polycystic ovary is sufficient; follicle distribution not required; polycystic ovaries without an ovulation disorder or androgen excess should not be considered PCOS.
- Dewailly D, Lujan ME, Carmina E, Cedars MI, Laven J, Norman RJ, Escobar-Morreale HF. Definition and significance of polycystic ovarian morphology: a task force report from the Androgen Excess and Polycystic Ovary Syndrome Society. Human Reproduction Update, 2014. Supports: PCOM in as many as 30% of young women; no significant health consequences of PCOM without other PCOS features, with the caveat on inconsistent definitions; OHSS risk with fertility injections; no shown effect on time to pregnancy; assessing PCOM preferably without recent pill use.
- Johnstone EB, Rosen MP, Neril R, Trevithick D, Sternfeld B, Murphy R, Addauan-Andersen C, McConnell D, Reijo Pera R, Cedars MI. The Polycystic Ovary Post-Rotterdam: A Common, Age-Dependent Finding in Ovulatory Women without Metabolic Significance. Journal of Clinical Endocrinology and Metabolism, 2010. Supports: 32% of 262 ovulatory women aged 25–45 with polycystic ovaries by follicle count, falling with age; no metabolic abnormalities; isolated polycystic ovaries not an indication for metabolic testing.
- Murphy MK, Hall JE, Adams JM, Lee H, Welt CK. Polycystic Ovarian Morphology in Normal Women Does Not Predict the Development of Polycystic Ovary Syndrome. Journal of Clinical Endocrinology and Metabolism, 2006. Supports: follow-up over a mean of about 8 years; 1 of 23 women with PCOM developed irregular periods and presumed PCOS; 11 no longer met PCOM criteria.
- Di Michele S, Fulghesu AM, Pittui E, Cordella M, Sicilia G, Mandurino G, D’Alterio MN, Vitale SG, Angioni S. Ultrasound Assessment in Polycystic Ovary Syndrome Diagnosis: From Origins to Future Perspectives—A Comprehensive Review. Biomedicines, 2025. Supports: scanning in the early follicular phase, or at random or a few days after a progesterone-induced bleed when periods are absent; repeating after a dominant follicle or cyst; transabdominal scans in women who are not sexually active and poorer images at higher weight; “string of pearls” description.
- Radiopaedia. String of pearls sign (ovary) (revised 2020) and Weerakkody Y, Knipe H, Fahrenhorst-Jones T, et al. Endometrial thickness (revised 2025). Radiology reference articles. Supports: the peripheral follicle pattern does not contribute to the diagnostic criteria; typical premenopausal endometrial thickness by cycle phase, as a guide only.
Related reads
- PCOS in India: symptoms, tests, treatment and daily care: the overview this page sits under. It covers diagnosis, every test and treatment in full.
- PCOD and PCOS meaning: full forms, what “polycystic” means and the new name PMOS.
- PCOS symptoms in women: the periods, skin and hair changes that matter more than a scan.
- PCOD vs PCOS: why Indian reports use two labels for one condition.
- Irregular periods and PCOS: what counts as irregular and when to worry.
- All PCOS articles: every Disha guide on PCOS in one place.
- BMI calculator with Indian cut-offs: a starting number for your weight. BMI is a screening number, not a test for PCOS.
