The final month of pregnancy is filled with excitement and anticipation.  So many preparations have been made for the big arrival.  Showers have been given, nurseries painted and cribs assembled, diapers purchased.  Then you wait.  You wait for some type of sign.  Is that a contraction?  Did I feel a trickle?  I swear I lost my mucous plug!  All signs that a baby might be on the way.

Each week during an office visit many soon to be moms look to us for a sign that things are getting close.  One frequent request is to have a cervical exam. That somehow a number means that the time is near.

Truth of the matter is that a number really doesn’t predict the arrival of a baby.

When a cervical exam is preformed your provider is looking for more than dilation of the cervix.  Many things need to happen before it’s all systems go.

One of the first subtle signals that a pregnancy is nearing its end is when the baby settles into the pelvis also known as engagement.  The head “drops” into the pelvis by a couple centimeters.   This can happen from a few days to weeks before the onset of labor.  Next the cervix softens, going from the consistency of the tip of your nose to soft and squishy like your lips.

As the uterus practices contracting, the cervix moves from behind the baby’s head, forward on top of its head closer to the opening of the vagina.   This is referred to as the position of the cervix.

The cervix has to thin out or efface.  I describe effacement as a mini donuts that starts out about 2 inches long and slowly thins out.  A cervix that is 50% effaced is about 1 inch thick.  100% effaced means that it is paper thin.

Usually the last thing to happen is cervical dilation.  Visualize the mini-donuts again.  The cervical opening starts out like a dimple and gradually opens.   1 centimeter is the size of your fingertip.  Two centimeters is the width of a penny.   Four centimeters a Ritz cracker.  Ten centimeters, the width of a bagel, is how much the cervix needs to dilate to pass over the baby’s head.

Most of these things occur prior to the onset of labor.  The cervical dilation is usually the last thing to happen and doesn’t until labor starts.  Most women are about two or three centimeters when they go into labor.  However, you may not be dilated at all or sit around for weeks at four centimeters. The number doesn’t indicate when labor is going to start.  It gives us a little reassurance that things are moving forward.

It gives some false reassurance that things will happen at any time and others despair that it never will.  So many women focus on a number as an indicator that the time is near.  Truth is, no one knows.  Usually it’s the woman I least expect that calls me in the night to tell me she’s in labor.