Hi!
My first pregnancy I had a short cervix (8mm) diagnosed at 28 weeks. We placed a pessary and managed to hold off the birth until 34 weeks, which was great.
Since you already have the cerclage, the effect should be pretty much the same.
Have you been having any symptons at all? Cramping, contractions, discharge? If so don't hesitate and go to the ER, make sure it has perinatal support / NICU.
Any chance you can stay off your feet these days? With that progressive shortening, it's not likely the cervix will elongate again. So the whole point is going to be holding on for as long as possible. Where I work (biggest MFM center in Lisbon Portugal) we'd stop measuring cervical length - we know it's really short, and the more we mess around in there the more we stimulate contractions.
I'm now 26+4 and also on bedrest for short cervix, so we'll be keeping each other company.
Hoping for all the best! Next big milestone is 28 weeks. Keep in mind that this week, for every day baby stays in utero we gain 2% survival without long-term complications (sequelae).
