The Myth of the Cervical Exam at the End of Pregnancy

Why It Might Not Be What You Think

Woman getting a vaginal exam and comfort from her partner
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There's a common misconception that by performing a cervical exam at the end of pregnancy, one can tell if labor will begin soon. This is not the case. One might argue, however, that having a cervical exam at the end of pregnancy allows a practitioner to help define when labor starts. An example might be that if a woman is four centimeters dilated in the office and later comes in with contractions and is still four centimeters, she is not in labor. The choice to have or not have a cervical exam—or which exams to have—is completely up to the patient.

Most practitioners will do an initial cervical exam at the beginning of pregnancy to perform a pap smear and other tests. Then, no further vaginal exams are performed until about the 35-37 week mark—unless complications arise that call for further testing or to assess the cervix. Typically, practitioners will also test for Group B Strep at this point. If your practitioner wants to perform a vaginal exam at every visit, you should probably question them as to why and for what benefit.

What a Cervical Exam Measures

Cervical exams can measure certain things:

Dilation

How far the cervix has opened; ten centimeters being the widest.

Ripeness

The consistency of the cervix. It starts out feeling firm like the tip of a nose, softens to feel like an ear lobe, and eventually softens further to feel like the inside of a cheek.

Effacement

This is how thin the cervix is. If you think of the cervix as funnel-like and measuring about two inches, you will see that fifty-percent effaced means that the cervix is now about 1 inch in length. As the cervix softens and dilates, the length decreases as well.

Station

This is the position of the baby in relation to the pelvis, measured in pluses and minuses. A baby who is at zero station is said to be engaged while a baby in the negative numbers is said to be floating. The positive numbers are the way out!

Position of the baby

By feeling the suture lines on the skull of the baby, where the four plates of bone haven't fused yet, a practitioner can tell which direction the baby is facing because the anterior and posterior fontanels (soft spots) are shaped differently. (This measurement is not used in the office because it is difficult to tell with minimal dilation and intact membranes.)

Position of the cervix

The cervix will move from being a more posterior cervix to an anterior cervix. Many women can tell when the cervix begins to move around because when a vaginal exam is performed it no longer feels like the cervix is located near her tonsils.

What a Cervical Exam Cannot Measure

What this equation leaves to be desired is something that is not always tangible. Many people try to use the information that is gathered from a cervical exam to predict things like when labor will begin or if the baby will fit through the pelvis. A cervical exam simply cannot measure these things.

Labor is not simply about a cervix that has dilated, softened or anything else. A woman's cervix can be very dilated and she still may not have her baby before her due date or even near her due date. Some women may walk around with a dilated cervix for weeks. Then there are others who don't dilate even 24 hours before birth. Cervical exams are just not accurate predictors of when labor will start.

Using a vaginal exam to predict advisability for a vaginal birth is usually not very accurate for several reasons. First of all, it leaves out the factor of labor and positioning. During labor, it's natural for the baby's head to mold and the mother's pelvis to move. If the cervical exam is performed in early pregnancy it also removes the knowledge of what hormones like relaxin will do to help make the pelvis—a moveable structure—be flexible. The only real exception to this is in the case of a very oddly structured pelvis. For example, a mother who was in a car accident and suffered a shattered pelvis or someone who might have a specific bone problem, which is more commonly seen where there is improper nutrition during the growing years.

Risks of Performing Cervical Exams

Vaginal exams can increase the risk of infection, even when done carefully and with sterile gloves. An internal exam may push the normal bacteria found in the vagina upwards towards the cervix. There is also increased risk of rupturing the membranes. Some practitioners routinely do what is called stripping the membranes, which simply separates the bag of waters from the cervix. The thought behind this is that it will stimulate the production of prostaglandins to help labor begin and irritate the cervix causing it to contract. This has not been shown to be effective for everyone and does have the aforementioned risks.

During labor, keeping vaginal exams to a minimum is a good idea, particularly if your membranes have already ruptured, so as to limit the risk of infection.

In the end, only you and your practitioner can decide what is right for your care in pregnancy. Some women refuse cervical exams altogether, some request to have them performed only after 40 weeks, every other week, or whatever she feels comfortable with.

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Article Sources
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