What is the latest international consensus definition for the ultrasound assessment of the PCO ?

The polycystic ovary should have at least one of the following: either 12 or more follicles measuring 2-9 mm in diameter or increased ovarian volume (>10 cm³). If there is evidence of a dominant follicle (>10 mm) or a corpus luteum, the scan should be repeated the next cycle.

The subjective appearance of polycystic ovaries should not be substituted for this definition. The follicle distribution should be omitted as well as the increase in stromal echogenicity and/or volume. Although the latter is specific to PCO, it has been shown that the measurement of the ovarian volume is a good surrogate for the quantification of the stroma clinical practice.

Only one ovary fitting this definition or a single occurrence of one of the above-mentioned criteria is sufficient to define the PCO. If there is evidence of a dominant follicle (>10 mm) or corpus luteum, the scan should be repeated the next cycle. The presence of abnormal cysts or ovar­ian asymmetry, perhaps suggesting a homogeneous cyst, necessitates fur­ther investigation.

This definition does not apply to women taking the oral contraceptive pill, as ovarian size is reduced, even though the polycystic appearance may persist.

A woman having PCO in the absence of an ovulation disorder or hyperan­drogenism (asymptomatic PCO) should not be considered as having PCOS, until more is known about this situation.

In addition to its role in the definition of PCO, ultrasound is helpful to pre­dict fertility outcome in patients with PCOS (response to clomifene citrate, risk for ovarian hyperstimulation syndrome (OHSS), decision for in vitro maturation of oocytes). It is recognised that the appearance of PCOs may be seen in women undergoing ovarian stimulation for IVF in the absence of overt signs of the PCO syndrome. Ultrasound also provides the opportunity to screen for endometrial hyperplasia following technical recommendations should be respected.