I have a cerclage now and had one in my previous pregnancy - both I was placed on pelvic rest - nothing in my vagina - no sex, no masturbation, no toys - NO ORGASM. It is not fun - trust me.... but I had some contractions at 24 weeks that were painful and I tore through my cerclage - so right now I only have a stitch in the 12 o'clock position - it has pulled through at 3, 6 and 9 o'clock. I am 33 weeks right now and take the progesterone shots weekly to help my cervix stay long - last measurement was 28 weeks around 2 cm... I am however 2cm dialated - which I have been since 24/25 weeks. I had my cerclage pulled at 35 weeks last time and hopefully the same thing this time so I can get some sex in before the baby is born!!!
I don't think that it would hinder it. If you are concerned though ask your doctor about what is safe for the cerclage.