It is possible that a 24 week cervix 20mm will last until full term, or it is possible that the labor will be preterm. 1. may last until full term: 24 weeks cervix 20mm can easily lead to preterm labor, although the best time for cervical cerclage is within 14-18 weeks, if under the guidance of the doctor 24 weeks can also be cerclage, the best cerclage surgery, and then need to rest in bed, prohibit strenuous exercise, prohibit sexual intercourse, it is possible to last until full term. 2. May be preterm labor: the cervical length of 30mm or more is normal, as long as less than 25mm there will be signs of preterm labor, so the cervix 20mm preterm labor is more likely, need to be under the guidance of the doctor to keep the baby well. Cervix 20mm at 24 weeks needs to be individualized by the doctor according to the specific situation of the pregnant woman, so as not to lead to preterm delivery.