Rotterdam criteria
According to the Rotterdam consensus,1 polycystic ovarian syndrome (PCOS) is defined by the presence of two of three of the following criteria: oligo‐anovulation, hyperandrogenism and polycystic ovaries (≥ 12 follicles measuring 2‐9 mm in diameter and/or an ovarian volume > 10 mL in at least one ovary). The sonographic criteria were based on a study published in 2003 by Jonard et al., 2 where patients with PCOS were found to have significantly more follicles in the 2‐5 mm range than a control group comprised of women with tubal or male factor infertility. The decision to set the cut‐off at 12 follicles measuring between 2 and 9 mm resulted from a compromise between specificity (99%) and sensitivity (75%), noting that narrowing the range to between 2 and 5 mm did not improve the diagnostic power. A suggestion was made to repeat the assessment in a subsequent cycle if the ovary was enlarged and its antral follicle count obscured by a dominant follicle (>10 mm) or a corpus luteum.3 There is no consensus on how to classify ovaries with a high follicle count when using oral contraception or other exogenous hormones or when there is evidence of a dominant follicle or corpus luteum in successive cycles.
Is the Rotterdam consensus still appropriate?
Over the 15 years since the Rotterdam consensus, increasing use of transvaginal assessment and technological improvements in ultrasound resolution have resulted in 20%–30% of regularly cycling, normo‐ovulatory women satisfying the Rotterdam criteria for polycystic ovarian morphology4 and even more in a younger demographic.5 The sonographic assessment has, over time, become the dominant indicator of PCOS and is often either overinterpreted or misinterpreted as a de facto diagnostic test, often ignoring the presence of a dominant follicle or corpus luteum. These women may then be inappropriately considered ‘polycystic’ without having the requisite clinical or biochemical correlates.
Post‐menarcheal teenagers almost always have at least one ovary with > 12 visible follicles and labelling them as ‘polycystic’ can lead to unnecessary investigations, inappropriate management and stigmatisation. The same is true for women with regular, ovulatory cycles attending ultrasound for reasons other than fertility assessment, who happen to have 15 visible antral follicles and a dominant follicle or corpus luteum. Being wrongfully labelled ‘polycystic’ may also adversely affect self‐esteem and influence women's choices around their diet and use of contraception.
So, is there a better way?
Over the past few years, the sonographic criteria embedded in the Rotterdam Consensus have been rightly challenged. In 2011, Dewailly6 studied 240 consecutive patients with mixed symptoms and recommended an ovary not be considered to have polycystic ovarian morphology until ≥ 19 follicles were noted, whilst Lujan et al.7 in 2013 studying 98 women with NIH classified PCOS and 70 normo‐ovulatory volunteers recommended a threshold at ≥ 26 follicles. The difference in recommended follicle numbers is explained by Dewailly excluding clinically normal patients with high follicle numbers from the control group. A meta‐analysis performed by the Androgen Excess and Polycystic Ovary Syndrome Society in 20148 found that the median follicle number per ovary (FNPO) in women of reproductive age is between 13 and 16 and strongly advocated increasing the threshold for polycystic ovarian morphology to ≥ 25 follicles. Use of ≥ 25 follicles is also supported by the International Society of Ultrasound in Obstetrics and Gynaecology Consensus Group.9, 10
Labelled or numbered?
Strictly, use of the term ‘polycystic’ in most contexts is incorrect. A cyst is defined as a pathological cavity having fluid or gaseous contents and ‘polycystic’ has the connotation of multiple pathological collections. A tertiary (antral) follicle that becomes visible is a physiological process and the number of them does not necessarily reflect a pathological process. In many cases, it may simply reflect a physiological increase in the number of visible immature follicles. We all have experience of the label ‘polycystic’ being a source of confusion, anxiety and occasionally resulting in unnecessary interventions. It is a term still poorly understood by many women – and their healthcare providers – with the quality of counselling and information provided to women varying greatly. Alternative terms are now also in use, such as ‘multifollicular’ when ultrasound criteria are satisfied and ‘hyperandrogenic anovulation’ when associated syndromic biochemical or clinical features are additionally present. This has resulted in further confusion for women and their doctors, and we strongly recommend avoiding the use of labelling in this setting.
Clinical practice points
Before interpreting the sonographic results, the menstrual cycle day, length and pattern should be ascertained along with hormone (particularly oral contraceptive) use, where the follicle count is clinically unreliable.
Record the FNPO as well as the total antral follicle count (AFC), especially in case of fertility treatment where the follicle numbers have implications for ovarian stimulation protocols and outcomes9 and describe the presence and dimensions of the dominant follicle or corpus luteum.
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Whilst trying to avoid unhelpful labelling, it is still necessary to classify the FNPO into clinically useful groups for consistency of counselling and management. They may be classified into low, normal (4–24 FNPO) and high follicle counts (Table 1).10
Women with an increased follicle count (≥ 25 FNPO) may be at higher risk for hyperandrogenic anovulation, and correlation with clinical and biochemical factors would be appropriate in this group.
Women with a low follicle count (< 4 FNPO, in the absence of contraception) are at an increased risk of menopause within 7 years.11
In the context of fertility treatment, a total AFC of > 20 follicles carries with it an increased risk of ovarian hyperstimulation syndrome (OHSS).12
Table 1.
Suggested classification to use in routine clinical practice in women with no exogenous hormone therapy. Table adapted from Martins et al9 and Coelho Neto et al.10
| Ovarian morphology | FNPO | Clinical interpretation |
|---|---|---|
| Low follicle count | 1–3 | Menopause potential increased within 7 years |
| Normal follicle count | 4–24 | Normal follicle count |
| High follicle count | ≥ 25 | Higher risk of hyperandrogenic anovulation |
References
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