I've had previous procedures in the past to remove pre cancerous cells so my cervix is monitored in pregnancy.
With my 1st baby it was 28mm at 19 weeks, which although was shorter, it wasn't dangerous so no further action was taken.
This time I was scanned at 14 weeks where it measured 23mm. Worrying but they said they'd just monitor for now. I saw them again at 16 weeks when it measured 19mm and she said I needed a stitch doing asap. She booked me in for 2 days later but then phoned 2 hours before I was due to go in to cancel and rearrange for a weeks time!!! 
I then got a phone call earlier this week delaying it by another day so it won't be done till this Friday when I'll be almost 18 weeks.
I've been taking it easy, stayed off work, not being lifting my 16 month old etc but am terrified it could just shorten dramatically overnight and feel the longer the leave it, the more risky the procedure is.
Does anybody have any advice? Has anybody got a cervix this short this early on??