Nae,
With my stitch and prev pregnancys that ended with abrupt cervix shortening my cervix with a stitch in was 3.5cm at 20 weeks. Prev scans on the pre term labour and rupture of membranes were 1.5 at 13 weeks and 1.8 at 18 weeks they thought that was normal!

From the point of 16 weeks the baby starts to put weight on the cervix due to its increasing size so as time goes on the cervical length should maintain and may shorten according to the week but not shorten significantly.

Your obst is right my gauge was 2.0cm and then I would of been hospitalised thankfully it never shortened past 2.9cm.

As long as they are monitoring you and they know your previous pregnancy history they should be aware of the importance of the scans. How often do you have us's? Aftern 30 weeks they became a little less determined to have me have them 2 weekly as it was a milestone I never that thought I would reach

Bec