Firstly this is for a friend not for me i've not touched drugs.
My friend is 21 and gave up drugs 6 months ago after being on them for about 18 months, mostly meow but also speed, coke, mdma, shrooms and ket. We were talking earlier about how amazing conception and stuff is when we thought about how a girl is born with all her eggs therefore her taking drugs could of damaged them, she knows it reduces her chance of getting pregnant she can live with that but she's now terrified if she does become pregnant then her baby could have something wrong with it due to her previously taking drugs, is this possible, if so how likely?
AFAIK there is no reason to think that recreational drug taking can damage existing eggs. I believe there is some evidence to suggest that it can impact on the healthy development of sperm, therefore some advise men to abstain from taking them for a full sperm life cycle (I think 90 days) before ttc. I don't have any links sorry.