HI, I have consived through IVF. Due to miscarriage in last pregency in 24 weeks after cereclage, my doctor suggested for cereclage before embriyo transfer. Now cereclage is in place at cervix lenght of 2.9-3 cm. Now I am 12.6 weeks of pregency and in NT scan cervix length is found  as 2 cm in ultrasound. How can we calculate this as full height of 2.9 + 2 cm ?. My doctor told after cereclege we measure it as 2 cm in length from the cereclage knot. I am in confuse about the length and is there any risk of preterm birth. What type of precautions I have to take care. Can any one please suggest on this.