It is around a woman’s 38th week of pregnancy. Her OB does a cervical exam and declares:
“You are 2 cm dilated, your baby will be here soon!”. The week passes and the next week and perhaps even the next week, but still no baby.
OR
It is around the 40th week of pregnancy and an expecting woman has had yet another cervical exam where the OB declared,”You are not dilated at all.”
Let me let you in on a secret, your cervix is not a crystal ball. It cannot predict when labor will start. Nor can it predict if you will deliver before, after or even on your due date. The cervix can do many wonderful things, but let’s not give the cervix more credit than it is due. A cervix cannot predict the future.
Having the cervix examined may satisfy mom’s curiosity and can be exciting. Obviously each bit of dilation that occurs before labor is less that must happen during labor. However if cervical change is found, and especially if the care provider adds the comment that labor will be soon, it can make the last weeks of pregnancy the longest of her life. Everyday becomes high alert for impending labor and each day that it doesn’t happen will be a disappointment. The woman may now feel each discomfort of late pregnancy more acutely and her family might even travel to be in town for the big day. However, instead of holding a baby they are all just staring at mom waiting for her to pop. These women may be encouraged to electively induce and they agree because they are mentally exhausted from being told the baby would be here any second.
On the other hand when a woman has an exam and nothing is happening, she may start to lose confidence in her body and feel that she will be pregnant forever. Even though it is completely normal for dilation not to occur until actual labor, these women are often made to feel that their bodies are not working correctly. Mom is discouraged and when the provider starts looking at induction (or in some cases surgery) dates, she agrees because obviously she will not go into labor on her own any time soon and in the back of her mind she thinks her body may not even be capable of spontaneous labor.
The cervix is a a unique creature. Some will naturally dilate prior to labor, some will not. Some will dilate and efface slowly over time; but many will only do so with the advent of contractions. The bottom line is that a cervical exam only tells the story of what is going on at the time of that exam. It tells nothing about what will happen…even later that day. A cervix does not need to reach a certain point for contractions to start, just the opposite. Contractions will open a cervix when the time is right no matter what that cervix has been up to prior to that moment.
There is no evidenced based reason for routinely doing cervical exams during the final weeks of pregnancy. Having them done is entirely up to each woman. In individual circumstances a vaginal exam can be helpful, but for the vast majority of women a cervix check provides no predictive clinical information and it is an uncomfortable and invasive procedure that actually carries some amount of risk. However, if you are curious and want to know what is happening in there, go for it, but don’t give your cervix more credit than it deserves!
(Note from Maria – This blog was originally published on my mommy blog Life in the Slow Lane circa 2006, then moved to my birth blog Belly Up Baby circa 2009 and now lives here….it is my most commonly read or quoted post! It has been adapted a bit over time but the basics are the same. You can now purchase a t-shirt with the quote, “Your Cervix is Not a Crystal Ball” at www.shopbirth.com )
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Maria Pokluda has been a doula serving expecting families in Dallas and Ft. Worth since 2007 and has helped hundreds of 
families have happy birth days. Maria was voted “Best Doula” by DFW Child the past five years and has a special passion for helping couples achieve VBACs. In 2011, Maria co-founded a doula training organization and trains doulas from around the world with BEST Doula Training. You can find information about Maria’s services or read her blog at greatexpectationsbirth.com