Do Cysts Reduce The Chance Of Pregnancy?

i m 33 yrs old ,married for more than a year.didn't conceive yet.my gynaec diagnosed me with PCOS,i was given letrozle 2.5 mg day 2-6,got three follicles 21mm,21mm,17mm on day 12.was given hcg injection.scan on day 15th shows 2 eggs releaes and 3rd follicle turned into cyst.doctor said there is 50/50 chance that i can conceive this month.she put me on duphaston 10mg b.d and aspirin 81mg,my question is is 2 eggs are released ,still there is just 50 % chance to get pregnant?is it because of cysyt?i don't have any cyst before starting letrozole.and i m on metformin 500 mg tds.