When you meet with your healthcare provider for your 20-week appointment, they’ll likely perform a transabdominal ultrasound. That’s the one where they squeeze cold gel onto your abdomen and move a probe over the surface of your skin to pick up imaging of your uterus. While that ultrasound can be helpful in seeing the size of your baby, it’s not particularly easy to see the size or length of your cervix from the abdomen, and you might not get a cervical length measurement.
Unless you’ve had a cervical surgery or a previous preterm delivery, your provider might not specifically look at your cervix or check to see if you have a short cervix – a cervix less than 2.5 cm long. The average range of a cervix during pregnancy is 3 to 5 cm, and that length will shorten as your pregnancy progresses. A short cervix before your 24th week of pregnancy is a predictor of preterm birth, which comes with serious risks. If you want to know whether you have a short cervix but you don’t have a history of preterm delivery, you may need to request a transvaginal ultrasound.
Unlike the abdominal ultrasound, which runs a probe on the surface of your skin to pick up images of your baby, a transvaginal ultrasound requires a probe to be inserted two to three inches into the vagina to get a picture of your cervix. It can create images of your reproductive organs and give your provider a clear picture of your cervical length. It takes 30 minutes to an hour, and it gives your healthcare provider the most accurate picture of your cervix and whether it puts you at risk of preterm delivery.
Talking to your provider
Cervical length can play a large part in determining a woman’s risk for preterm delivery, and if a short cervix is caught early in a pregnancy, there are some things your provider can do to reduce your risk of early delivery. Because of this, it’s likely worth asking your healthcare provider to look at your cervical length between your 16th and 24th week of pregnancy. If it’s not clear over the abdominal ultrasound whether you have a short cervix, consider requesting a transvaginal ultrasound so you and your healthcare provider can have a clearer understanding of your risk for preterm delivery.
- “Cervical insufficiency and short cervix.” March of Dimes. March of Dimes Foundation. August 2015. Web.
- “Preterm (Premature) Labor and Birth.” ACOG. American College of Obstetricians and Gynecologists. November 2016. Web.
- “Management of Pregnancies With Cervical Shortening: A Very Short Cervix Is a Very Big Problem.” Obstetrics & Gynecology. U.S. National Library of Medicine. National Institutes of Health. 2009. Web.
- “Transvaginal ultrasound.” MedlinePlus. U.S. National Library of Medicine. May 16, 2016. Web.