Labor Progression Jargon

There are some terms that get used a lot in late pregnancy describing cervical condition and labor progression. The most common of these terms are: dilation, effacement, and station. Your ob will do unspeakable things to do you determine where you stand cervically at the end of your pregnancy.

The cervix is the lower portion of the uterus. If a normal cervix resembles the neck of a bottle turned upside down, dilation refers to the width of the opening of the bottleneck. A cervix that is 10 cm dilated is ready to pass baby through. Using the same bottle analogy, effacement refers to how long or thick the bottleneck is. A normal cervix is around 3.5 cm thick during pregnancy (0% effaced), and an effaced cervix is thinner by varying degrees. A cervix that is 50% effaced is half its original thickness. A fully effaced cervix (100%) is ready to pass baby through.

The concept of station denotes the degree of engagement of the fetal head as it navigates the maternal pelvis. Station is reported as a number between -4 and +4, with zero (0) station referring to the fetal head being level with the ischial spines.

To put some things in perspective, my physician will optionally induce labor if the cervix is 2-3 cm dilated at 39 weeks. You can request an epidural during labor at 4 cm.

Any progressive cervical change usually means you are closer to baby, however, cervical changes are not an accurate predictor of when you will go into labor. A woman can be dilated and effaced to varying degrees for several weeks before going into labor. Your physician may make an educated guess based as to when you are likely to go into labor based on these factors, but science hasn't been able to completely pin Mother Nature down on this one yet.