A short cervix is one that is less than 25mm (2.5cm) long at around 20 weeks of pregnancy. The shorter the cervix, the higher the risk of an early birth (earlier than 37 weeks pregnancy) . Risk factors associated with having a short cervix include previously having a preterm birth or previously having a procedure on your cervix where a part of your cervix was removed. A short cervix is diagnosed using ultrasound. Most women with a short cervix still give birth on time, but if you have a higher-than-average risk of having your baby early, it is important to know this ahead of time, before labor begins, so that you and your health team can be prepared. A short cervix can be managed during pregnancy with rest, progesterone medicine, or a procedure called cervical cerclage. If a clinician thinks that a woman may have a short cervix, they may begin checking the length via transvaginal ultrasound between weeks 16 and 20. If the cervix is less than 25 mm long (about 1 inch), doctors generally consider it to be short. However, some doctors use different standards, and they may consider a length of 20–30 mm to be short.