Cervical Os And Its Role In Childbirth

You would be aware of the cervix, especially during pregnancy. How about cervical os? When I heard it for the first time, I mistook the ‘os’ to stand for an operating system! But I figured out pretty soon that it is an anatomical structure.

A cervical os is simply an opening to the cervix while the cervix is the entrance to the uterus. If you can imagine a funnel, you can make the analogy. If you consider the tube and the cervix, you will understand that there is an internal cervical os and an external cervical os. The internal os is closest to your baby while the external os is the farthest. Now consider another analogy. If your mouth is the opening to your digestive system, so are your lips the opening to your mouth. This could very well explain to you how a cervical os is different from a cervix.

It is the cervical os that acts as the opening to the uterus and allows the sperm to enter the uterus during ovulation. The opening and the closing of the cervical os is very subtle. It is the cervical os that effaces or thins out and dilates or opens during labor and allows the birth of your baby. The thinning and effacement can be imagined as the internal and the external cervical os coming closer together. It’s a phenomenon common in pregnancy and during labor. You can tell the degree of effacement regarding percentages. If your cervix has not effaced yet, that is it is at 0% effacement; it means that it hasn’t started thinning yet. If your cervix is 100% effaced, it means the cervix has gone very thin. On the other hand, the dilation of the cervix can be measured in centimeters. If the cervix is dilated to ten centimeters, it means that it is fully dilated. In fact, both the dilation and effacement happen simultaneously but might not happen at the same pace. Usually, effacement and dilation occur with the contractions of labor.

While you may be obsessed with the uterus, you will pay less attention to what the cervix is, let alone what a cervical os is. Your cervix might take most of your attention only in case of emergencies, such as in preterm labor when the cervix begins to dilate too early. The other times could be when your cervix is obstructed with the placenta as in placenta previa thereby blocking your baby’s birth.

What happens when the cervix is completely closed beyond the due date? Ideally, the cervix thins out in anticipation of delivery, but it might as well not show any signs and remain in the same condition as in pre-delivery. Such a closure can be a common feature especially in the first pregnancy whereby the cervix may remain closed until the onset of labor despite the effacement happening. The cervix ‘ripens’ or softens in most women at around the 36th week or by the 42nd week.

If the cervix does not open or does not ripen for at least two weeks beyond the due date, then your practitioner might recommend that you be induced. It is not safe to have your baby for over two weeks beyond the due date in your womb. Your practitioner might advise you of the risks involved if you don’t allow for labor induction. Therefore it might be good that you are aware of the benefits of labor induction and that you agree to it.

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