A review of the evidence of Coenzyme Q10 and its role in fertility published in August in Frontiers in Cell and Developmental Biology found that CoQ10 supplementation can be beneficial due to its protective effect on female fertility, including in PCOS.

CoQ10 is a lipid-soluble benzoquinone, which is involved in the metabolism of mitochondrial energy and also in regulating oxidative stress and reducing reactive oxygen species. Through these mechanisms, CoQ10 improves oocyte quality, ovarian function, and mitochondrial efficiency, and can support the assisted reproductive treatment process.

The studies examined as part of this review are all small-scale studies (maximum n=185), and the dosage varies from 30mg to 200mg per day, and duration varied too. Despite this, studies showed improvements in egg number, egg quality, and, in the case of one study, implantation rates. Whilst there is not enough evidence to make general clinical recommendations, and the authors acknowledge a need for further research, this is an area to watch in the future of fertility health. 

You can read the full paper on PubMed here