Effacement and Dilation Explained

In the final weeks of pregnancy, an expectant mother’s body begins its natural preparation for labor and delivery. Among the early signs of labor are effacement and dilation, important changes that occur to the cervix and work together to make it possible for the baby to safely and smoothly come out of its mother’s uterus. 

What is Cervical Effacement? 

When a woman isn’t pregnant, and during most of a pregnancy as well, her cervix is long and thick. In actual measurements, a normal cervix is not really very long, just 3-5 centimeters (1-2”) in length. In the final weeks of pregnancy, as the lower part of the uterus gets ready for the baby to come out, the cervix starts to get shorter and thinner. This process is called effacement. As the cervix becomes more and more effaced, it gets shorter and shorter and increasingly “pulled up”, eventually seeming to become part of the lower uterus (the cervix itself almost seems to disappear). Effacement is also sometimes referred to as “ripening” or “thinning out.” 

As the due date nears, the baby’s head drops down and the mother’s uterus begins to contract; this, combined with effacement and dilation, can cause pressure and cramp-like pains. Women, especially those experiencing their first pregnancy, might think this means they’re going into active labor, but these “false labor” or Braxton Hicks contractions are just early signs that the process has begun. It usually takes several weeks for the cervix to become fully effaced. (If a woman is having her first baby, her cervix will probably efface before it dilates; in subsequent pregnancies the cervix may dilate first, then efface.)

During the final weeks of pregnancy, your health care provider will examine the cervix and can report on these changes. Cervical effacement is measured in percentages – e.g., no changes means 0% effaced, when the cervix is half its normal thickness, it’s 50% effaced. When the cervix is 100% effaced, that means it’s completely thinned out, leaving just the opening at the bottom of the uterus for the baby to come out. 

Readying for Baby: Dilation

As the cervix effaces and thins out, it also begins to stretch and open. This is called dilation. This widening and opening makes it easier for the baby’s head and the rest of its body to pass through from the uterus into the vaginal canal for delivery. 

The degree of dilation is measured in centimeters. For most of your pregnancy, the cervix will be at zero centimeters, closed and not at all dilated, keeping the baby safe and growing inside. During active labor, your health care provider will measure the level of dilation by inserting a gloved finger into your vagina. Sometimes dilation is also referred to in “fingers,” based on the manual exam, e.g., “she’s two fingers dilated.” One finger is the rough equivalent of one centimeter, but this is a more subjective measure, since finger size varies, especially between male and female examiners. 

The progression of labor is measured by the advancing dilation of the expectant mother’s cervix. It’s generally estimated that the cervix will dilate one centimeter during each hour of labor, but this cannot be generalized for every woman or every pregnancy. 0-4 centimeters dilation is considered early labor, and it’s not uncommon for a woman to be up to 2 centimeters dilated several weeks before giving birth. Dilation of 4-7 centimeters occurs during active labor. 7-10 centimeters is the transition phase (shift from active labor to the final phase, delivery), and when your cervix is at 10 centimeters (about the size of a newborn’s head), it’s considered fully dilated and you’re ready to give birth. 

4.33669
Average: 4.3 (894 votes)
 

2 comments

By SurvivalDad on 03/18/15 at 12:57 pm

Good article. I would think it would be hard to not be in active labor at 4cm. We were at the hospital in active labor @ 3cm - 4cm every time. Does dila  ...

By bellasmom18 on 01/20/12 at 1:59 pm

how? At 4cm you are in active labor wether you feel the contractions or not.

By justjaQ on 12/12/11 at 7:29 pm

i've been 5 and 6 cm without being in active labour.

Today on JustMommies

Best Bottles for Nursing Babies

f you’re in the market for baby bottles, you have particular needs if you’re a breastfeeding mom. You want to look for a bottle that mimics the motion, flow and feeling of breastfeeding to avoid “nipple confusion”.

Best Last Names for First Names

Giving a child a family name has long been a popular tradition. Often boys are named after their fathers or girls after a grandmother or aunt. However, new parents create different trends.

Gender Identity: Raising a Transgender Youth

According to a report by the BBC, "the number of children aged 10 and under who have been referred [for] support services to help deal with transgender feelings has more than quadrupled in the last six years."

When Parents Aren't on the Same Page

Think back to the time before you became a parent: Maybe you talked with your partner about having children. Yet, your “parenting styles” may not have entered the conversation.

From The Message Boards

Baby Name Games

New Generation Caf 3

The grandkids now have kids. Roll the 6 sided dice, flip for genders. Last names are your choice....

Baby Name Games

New Generation Caf 2

Roll the 8 sided dice for each child. Flip a coin for genders. To name spouses and children, go ....

Baby Name Games

New Generation Caf 1

Roll the 8 sided dice to find out how many kids you have, flip a coin to find out genders. Each chi...

Unplanned Pregnancy

19 and pregnant, is my decision a horrible one?

my name is Lilly, im 19, in college, im taking this year off to work fulltime up to my due date in s...

Ectopic Pregnancy Experiences

Possible ectopic dates 7 wks nothing in uterus

Had my last period dec 23rd. Went to GP on 7th Feb after 2 weak positives HPT. In clinic urine test...