Cervical length is not used to predict due dates because it is unreliable. Its measurement is used to assess the risk of preterm labor in women with a shortened cervix, explains WebMD. Cervical effacement, or thinning, is used for tracking the process of labor, according to Mayo Clinic.
Cervical length is only used for predicting premature labor between 16 and 32 weeks because all women in labor have cervical shortening, according to the National Center for Biotechnology Information. The average cervical length between 20 and 30 weeks gestation is 35 millimeters; this group represents a low risk for premature labor. Between 28 and 30 weeks of gestation, women with a cervical length of 25 millimeters or less have been shown to have a significant risk of pre-term labor, explains the National Center for Biotechnology Information.
Preterm labor occurs before 37 weeks of gestation and is a complication in 12 percent of all pregnancies. It accounts for 75 to 95 percent of all neonatal deaths, which is why assessing cervical length in the presence of other risk factors is important, states the National Center for Biotechnology Information.
Prevention of premature labor in the presence of a short cervix depends on the physician and the risk. Many obstetricians recommend bed rest, the use of tocolytics or the placement of a cervical cerclage. A cerclage is a surgical stitch placed in the opening of the cervix between 13 and 15 weeks to prevent pregnancy loss. It is often used in cases of recurrent pregnancy loss or cervical insufficiency, according to the National Center for Biotechnology Information.