To dilate something means to widen or enlarge something. In medical literature, the word ‘dilated’ finds frequent usage in a variety of cases – from widening of the pupil of an eye to opening up of a narrowed blood vessel. However, it is maximally used in the Obstetrics and Gynecology Department where much depends on the ‘dilation’ of the cervix.
What do you mean by cervical dilation?
Cervical dilation (also referred to as cervical dilatation) is the opening of the cervix as the body prepares itself for childbirth. Normally, the cervix, which separates the uterus from the vagina, is hard and closed, thereby helping to protect the growing fetus from the harsh environment outside. As the time for your delivery draws near, the body undergoes several changes while getting ready for the big event.
Likewise, the cervix also widens and thins out so as to make it easier for the baby to come out of the womb. Imagine it to be opening of the door of the womb for the baby to pass through safely and smoothly. This widening up of the cervix is called cervical dilation.
Why does cervical dilation occur?
Let us first appreciate the problem that would have arisen had the cervix not dilated during delivery. Normally, the cervix is firm and almost non-stretchable. During pregnancy, a mucus plug is formed that shuts off the internal environment from the outside. So if the growing baby is to be delivered, it will face obstruction not only because of the mucus plug but also because of the non-stretchable, narrow cervix. This will lead to abortions in a majority of cases.
It is, therefore, understandable why the cervix has to thin out and widen during labor. It is believed that both hormones and pressure from the baby’s head play significant roles to bring about dilation of the cervix.
As the baby drops down to the pelvis towards the end of pregnancy period, its head presses on the cervix. As the pressure rises gradually, the body is ordered to release a hormone, oxytocin that causes contractions. These contractions push the fetus further down the cervix, resulting in dilation of that part. The constant pressure, in turn, causes more contractions. A vicious cycle continues till the baby is safely delivered.
How is cervical dilation measured?
The unit of measurement for cervical dilation is centimeters. Dilation ranges from 0 cm to 10 cm – the former implies no dilation while the latter means the cervix has fully dilated. During a vaginal examination, cervical dilation is measured by how many finger widths fit into the cervical opening. One finger tip corresponds to 1 cm dilation and 2 finger tips correspond to 2 cm dilation. If two fingers can stretch wide, it means further dilation has taken place.
It is normal for the cervix to open up to as much as 3 cm in the later stages of pregnancy, but it is only during labor, that the figure rises to 6 cm, courtesy repeated contractions.
Contractions and dilations up to 5 cm can be collectively referred to as early labor. This indicates that the countdown for your delivery has begun, but there’s no certainty about when it will happen. The contractions at this stage are characteristically mild to moderate, and the process of thinning and softening of the cervix has already begun.
Active labor implies your cervix has dilated 6-7 cm. The contractions are likely to pick up at this stage and you may experience periodical pain during those episodes. The cervix dilates at a faster rate and moves towards the transition phase (8 – 10 cm dilation).
Once 10 cm mark is reached, you are likely to hear your doctor tell you that you are ‘ready to push’. This means, the cervix has completely dilated and your baby is ready to be delivered into the world.
What you need to remember about cervical dilation
Every labor is different and every woman dilates at a different rate. Dilation of the cervix, therefore, is not at all a reliable indicator of when you are likely to go into labor or how quickly it will progress.
You may have a few centimeters of dilation weeks before you go into labor. On the other hand, you may go into labor hours after having a completely closed cervix. There are quite a few labor signs that are considered to be more reliable in this regard.