Preterm Labor and Short Cervix

Topic Overview

During pregnancy, the cervix is a closed and sealed tunnel between the uterus and the vagina. Before or during labor and delivery, the cervix stretches and flattens (effacement). At 24 weeks of pregnancy, the average cervix is about 35 mm (1.4 in.) long.^{footnote 1}

A short cervix has a length of less than 25 mm (1 in.). Women with a short cervix may have an increased risk of preterm birth. ^{footnote 2}

How is it treated?

If this is your first pregnancy or if you have never had a preterm birth, having a shortened cervix may not change the way your doctor treats your pregnancy. But if you have a very short cervix, 20 mm (0.8 in.) or less, your doctor may offer you medicine to help prevent preterm birth.^{footnote 2}

If you have had a preterm birth, you may already be taking medicine (such as progesterone shots), so your doctor may consider other treatments for a short cervix, such as a cerclage, to prevent preterm birth.^{footnote 2}

If you learn that you are at high risk of preterm birth, make sure that you know the symptoms of preterm labor and that you know what to do if you have them.