Hi
If you look HERE, there's a podcast from someone in the ABA who discusses IVF and breastfeeding (No. 22)
Is your wife having regular, ovulatory cycles? If so, then breastfeeding is not affecting her fertility (women can and do conceive while breastfeeding). Some doctors will tell you you need to wean, some will say it doesn't matter - the bottom line is that it depends and I dont' think anyone can really say with any certainty. Obviously, if it's still early on in the breastfeeding relationship, and/or cycles haven't resumed, then it may well be an issue.

I was still feeding DS when we returned to IVF to conceive DD. I had thought I would need to wean, but discovered otherwise and continued. I h ad to do an HRT FET cycle (not sure what you guys are doing) and the estrogen pills knocked my supply out. DS continued feeding till around 9-10 weeks before weaning himself. Obviously it had no effect on the cycle, and I know of at least one other on BB who continued feeding through her IVF cycle (in fact I think she might be tandem feedign still... not sure). The woman in the podcast also fed through IVF cycles.

The drugs used during IVF (depending on your protocol) can affect supply. The pregnancy can also decrease supply, but it varies from person to person and there is usually still some milk produced - some toddlers will wean themselves, some will continue anyway.

Good luck to you and your wife!!