Hi Carly, I can't speak for personal medical advice given to you, but I can say that baby aspirin (75mg) seems to be the 'catch all' advice that has been given to everyone for yonks. I've taken it pre-pg and during pg (can't say whether it worked or not, that pg got further than the first 2, but was Turners Syndrome so nothing could have saved it, in the end). St Mary's want me to take it again (150mg) if I get a positive TEG test after about 7 weeks.
Profs Quenby and Brosens see things differently. Their research seems to say that this advice is unhelpful and out of date. They are still doing research into implantation, and, by providing a sample of uterine tissue, anyone who goes to their clinic contributes to that research. I wouldn't be surprised that general advice about aspirin changes in years to come.
I'm no doctor, but what Prof Brosens told me yesterday makes sense. You can go to their clinic after 1x MC I think, and they want to see people between 7-10 days after OV, who are definitely not pg. They will want you to have a uterine lining thickness of about 9mm to get a good sample (I only had 7mm, so samples may not be any good - but last year I was only 2.2mm, so I was pleased that was improving).
It costs 360 pounds and you get a follow up consultation over the phone. All the meds are on the NHS, its just the procedure and consultation you pay for. The test is quite uncomfortable, but nothing a paracetamol won't fix.
I hope this info is helpful, and I haven't alarmed anyone on aspirin.