How can ovary cyst affect fertility?

Depends: Women with polycystic ovarian disease tend to have fertility difficulties. They also have excessive male hormones or androgens that can prevent fertility. Single ovarian cyst however may not have any impact on fertility. There are treatments for polycystic Ovarian Disease.

PCOS: IN polycystic ovary syndrome, hormones are stuck on the ON position. Fat, which contains the cholesterol precursor of estrogen and progesterone, leads to an overabundance of these. 1) they tend to keep the hormonal system ON 2) they break down to testosterone and further perturb normal hormonal balance 3) fertility is inhibited. http://www.nerdpocalypse.net/diseases/PCOS.html