Short cervix. Any risk thereof?

         The Doc admitted her in a ward and given heavy doses to induce labour pain. It took aroundthree hour to deliver the baby normally.             CURRENT CASE   1.         Conceived- 13 Dec 16 (First date of last period)   2.         We had NO sexual intercourse. Age of wife- 28 Yrs, Wg- 64 Kg   3.         Everything was normal till 06 Mar 17 i.e. 12th week of pregnancy. Our new Doctor (Army Hospital) had the vaginal ultrasound and recommended the followings:-               (a)       Baby is ok             (b)       Cx length- 3.3 Cm             (c)        Progesterone shot- weekly (injection)             (d)       Progesterone Tab 200mg 1 OD             (e)       Weekly review for Cx length measurement             (f)        Cercelage, if required at around 16 Week   Question to You.    Is the Cx is really incompetent? Is cercelage is helpful in this case? What is % of success of this Stretches? Any Risk thereof? And your valuable opinion.