Some women don't have problems at all, because the baby latches onto your areola and will draw out the nipple as they nurse. If you can though, it wouldn't hurt to get in touch with your local La Leche League or lactation consultant before the birth, so you have someone to call if you do have problems.
If you end up having a low milk supply, there are plenty of herbs and natural ways to increase it. You can educate yourself now though on what to look for and what you can do if it does happen. Here's a link I found on PCOS and breastfeeding:
kellymom.com :: Breastfeeding and Polycystic Ovarian Syndrome (PCOS)
If you have an oversupply, it's not really anything to worry about. I had a major oversupply with my first daughter and it was a pain to deal with (literally) but it didn't cause any major problems.