PCOS is the primary cause of anovulation in women of reproductive age. Anovulation occurs when the ovary does not release an oocyte (egg) during the menstrual cycle. Most women will have the occasional anovulatory cycle, without any underlying issue. However, 70-80% of women with PCOS will have fertility issues, usually due to persistent oligo- or anovulation.
If your periods are irregular, anovulation might be one of the first things your doctor considers. However, some women continue to have regular periods and in these cases diagnosing a cycle as anovulatory can be more of a challenge. The only way to clinically diagnose anovulation is to measure serum progesterone levels. Immediately after ovulation, progesterone levels rise markedly. If levels do not increase, the cycle is assumed to be anovulatory. Measurements should be taken over a number of cycles to ascertain whether ovulation is occurring regularly or not.
Fertility issues in isolation are insufficient grounds on which to diagnose PCOS; other symptoms also need to be present.