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I would have it done if I were you - over the space of my second pregnancy, I went from having a normal smear to CIN3. Prior to that I had 10 years worth of fluctuating smear test results, from CIN 1 back to normal again, with smear tests every 6-12 months. After the LLETZ treatment - normal results ever since. It's not fun thinking that despite what you are told about CIN abnormalities occurring slowly, that actually they either regularly miss them when they do smear tests, or that the cell changes can become severe very rapidly!!
Just seen your bit about miscarriage - ask at your after care appointment how much they removed. That's what is the important information. As I said, they removed a huge chunk of my cervix and no one told me. Was referred to a consultant as routine by my midwife as I'd had the LLETZ in the previous two years, and it took weeks. When I got there, it was the first time someone had read my notes since the procedure and he was very busy, organising scans to check things and talking about cervical stitches. However my cervix had regrown on its own, and it was fine, but if I'd known how much they'd taken off I could have had those extra checks a lot earlier.