Cervical length is the length between the internal cervical os and the external cervical os. This length is accurately measured using a transvaginal  ultrasound  on an empty bladder.  A full bladder can increase the cervical length especially when using a transvaginal ultrasound.

 
The normal length of the cervix during pregnancy is 3cm or greater. The length may vary depending on how full your bladder was during the ultrasound and whether the ultrasound was done vaginally or not. This length gradually begins to shorten around 32 to 34 weeks.

The cervix is usually closed and rigid before pregnancy. During pregnancy it gradually soften, decrease in length (efface) and open ( dilate ). These changes  occur as your baby grows and helps prepare you for delivery. If your cervix starts to open too soon, it can cause premature delivery.
 

What are some of the factor that affect cervical length ?

 
Factors that may affect cervical length include the following :

• cervical incompetence
• inflammation of the uterine wall
• infection
• an over distended uterus ( uterus that has stretched too far
• complications caused by bleeding during pregnancy
• biological differences among women

 
If you experience signs of preterm labor such as

• constant low, dull back ache
• frequent or regular contractions
• vaginal spotting
• pelvic pressure

 
Your health care provider will do a pelvic examination to determine if your cervix has began to open. He will also do an ultrasound to determine the length of your cervix.

If you are already in preterm labor, your health care provider will discuss the risks and benefits of  delaying or stopping labor. H e may also suggest a cervical cerclage if you are not in active labor and meet the criteria for this procedure.

If you have any concerns about your cervical length during pregnancy, please discuss it with your health care provider. He will address all your worries.