Week 20 - Cervical Insufficiency
This term is used to describe a cervix that is shorter than your OB would like. Typically 3.5 cm or more of tissue separates your baby from entry to the outside world, and when that length is shorter, OBs worry about preterm labor. A very worrisome length is 2.5 cm or less and I fall in the less worrisome, but nonetheless "watchful" category of 3.1 cm. The measurement of your cervix is done by an ultrasound technician at 20 weeks.
Cervical Insufficiency can lead to preterm labor. If doctors catch it early enough (13- 16 weeks), your cervix gets a stitch called a cerclage and you go on bedrest. Not sure how they catch it early if they routinely measure for it at 20 weeks.