There's a common misconception that by performing a cervical exam at the end of pregnancy, one can tell if labor will begin soon or if vaginal birth is recommended or not. This is not the case.

However, a cervical exam at this stage does allow a practitioner to determine dilation and possibly the position of the baby, which can help define when labor actually does (or did) start.

Overview

Most practitioners will do an initial cervical exam at the beginning of pregnancy to perform a Pap smear and other tests. Then, no further cervical exams are performed until about the 35th- to 37th-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.﻿﻿

It's important to note that performing a cervical exam is not risk-free. They may increase the risk of vaginal infection or could possibly result in the premature rupture of membranes.﻿﻿ If your practitioner wants to perform a cervical exam at every visit, question them as to why and for what benefit.

The choice to have a cervical exam—or which exams to have—is completely up to you.

Purpose

Cervical exams can measure certain things that can give a sense that labor may be coming soon, but none of these are surefire predictors of when exactly it will begin. Cervical exams are also subjective by nature and may not be entirely consistent among practitioners.﻿﻿

They are employed to evaluate the following:﻿﻿

Dilation: Referring to how wide the cervix has opened (10 centimeters being the widest)

Referring to how wide the cervix has opened (10 centimeters being the widest) Ripeness: This refers to 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.

This refers to 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 2 inches long, you will see that 50-percent effaced means that the cervix is now about 1 inch in length. As the cervix softens and dilates, the length decreases as well.

This is how thin the cervix is. If you think of the cervix as funnel-like and measuring about 2 inches long, you will see that 50-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!

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.)

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 further back in the body toward the front, or from posterior to anterior.

Limitations

What this examination 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.

A pregnant person'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 may walk around with a dilated cervix for weeks. There are others who don't dilate even 24 hours before birth.

A cervical exam can tell you many things, but unfortunately not when your baby is on the way.

Likewise, and for several reasons, they're not predictive of whether a vaginal birth is advisable. For starters, the exam doesn't factor in 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 happens too early, it does not take into account what hormones like relaxin will do to help make the pelvis—a moveable structure—become more flexible.

The only real exception to this advisability recommendation 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 when there is improper nutrition during the growing years.﻿﻿

Risks

Cervical exams can increase the risk of infection, even when performed carefully and with sterile gloves. An internal exam may push the normal bacteria found in the vagina up toward the cervix. There is also an increased risk of rupturing the membranes by applying too much pressure on the cervix.﻿﻿

Some practitioners routinely do what is called stripping the membranes, which simply separates the bag of waters from the cervix. The intention is that membrane stripping 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 still carries the aforementioned risks.﻿﻿

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

A Word From Verywell

You and your practitioner should work together to decide what is right for your care during pregnancy, weighing the benefits against the risks. Some pregnant women refuse cervical exams altogether, while others request to have them performed only after 40 weeks.