question: I have just had my fourth failed IVF attempt. It took three attempts and no fertilisation before we were advised to do a fragmentation test on the sperm and my husband fragmentation is 61.1%. We got a donor and just had another cycle which unfortunately failed - had one grade 5 embyro and one grade 4 replaced on day 5, but they didn t implant. I am on carbimazole for a overactive thyroid which is stable the doctor tells me(taking 5mg every second day and 10mg the others) would this affect my chances of embyro implantation??