If you have mature follicles do they always release?

Rachael

Had 4 possible follices on my day 12 scan (18mm, 16mm, and 2 13mm) - we chose not to trigger in hopes of some of the smaller ones maturing and the possibility of more being released in theory giving us a better chance of conceiving. Is the problem with pcos that they don’t release or they never get mature enough to release?