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In order for the baby to be born, the strong and firm muscles forming the cervix need to soften, stretch and thin out or effaced and open to allow the baby to move down from the uterus and into the birthing tract. Prostaglandins are chemicals produced by the body towards the end of pregnancy which softens the cervix and helps it dilate. This process is called effacement.
What is Effacement of the Cervix
In the last weeks of pregnancy, you are checked for effacement which is measured in percentages. Once the baby’s head is stationed it starts to drop closer to the cervix which prepares itself for delivery. When there are no changes to the cervix it is called 0% effacement. The cervix which is normally 2-3 cm long begins to shorten to 1cm at the onset of labour, softens and becomes thinner or effaces gradually. This process is called effacement of the cervix and you are said to be 50% effaced in pregnancy. Other terms used for this process is “cervical thinning” and “ripening” of the cervix.
How to Measure Cervical Effacement
Effacement is measured in percentages. During pregnancy, there are no changes to the tightly closed cervix and it is called 0% effaced cervix. As the cervix softens, thins and is pulled around the baby’s head it gets to half the normal thickness or 50% cervical dilation and effacement with dilation of 1-2 cm. When 100% effaced, the cervix is completely thinned out and delivery is around the corner. The dilation or stretching and opening of the cervix are measured in centimetres. When completely dilated the opening is 10 cm and you are ready for a vaginal delivery.
Signs and Symptoms of Effacement
Changes to the cervix are checked during a pelvic exam from the onset of labour. During labour, your effaced cervix gets shorter and thinner to stretch and open around your baby’s head. Both dilation and effacement measure the progress in labour due to effective contractions of the uterus.
At the onset of labour, irregular contractions with long periods in between happen to allow cervical dilation of 1cm per hour. At 2 cm dilation, the cervix begins to open and the contractions move the baby downwards. At 6 cm dilation, you will experience more regular and frequent contractions. Finally, at 10 cm dilation, the cervix is 100% effaced and long continuous contractions signal active labour has begun to start pushing your baby out.
The “station” is recorded as a number between -5 and +5 and indicates the position of your baby’s head . -5 to -1-station means that the head isn’t engaged in the pelvis, 0-station would indicate the head is “engaged” and has entered the vaginal canal while 1 to +4-station would mean the baby is progressing down the vaginal canal. At +5-station your baby is crowning. Even if dilation is complete, the mother should not push until 0-station meaning the head is engaged in the canal.
First-time mothers are 100% effaced before dilation begins. Women who have birthed before can be dilated before effacement is complete.
Cervix Dilation during Labour and Birth