Picture of the cervix opening during childbirth

The cervical opening is medically known as the dilation of the cervical opening. Under normal circumstances, the cervix is ​​dilated to about the distance of a fingertip. As the labor progresses, the cervix gradually expands until it opens to allow a normal-sized fetus to pass through, which is 10 cm in diameter. The whole process is called cervical dilation.

The cervix is ​​about 2 cm long and is a muscular tube connecting the vagina and the uterus. The contraction of the uterus of pregnant women during labor intensifies, which promotes the expansion of muscles and fiber tissues around the cervical opening. At the same time, the fetus enters the pelvis, causing the cervical opening to gradually expand, and the cervical canal will shorten until it disappears.

When does the cervix open?

The entire process of the cervical opening from shrinking to expanding will last a long time. Generally, in the second week of pregnancy in September, the cervix begins to shrink and expand, a process also called cervical formation, and then the cervix begins to dilate.

The dilation of the cervix is ​​the first stage of labor, which is divided into two stages: the dangerous period and the active period according to the dilation status.

Dangerous period (from original to 3 cm)

As the uterine contractions gradually intensify, the cervical opening gradually opens and the expansion rate is relatively slow, taking about 8 hours on average. The rate of cervical dilation in primiparas is much faster than that in primiparas, because women who are pregnant for the first time need to have their cervix dilate before they can start to expand, while women who have already given birth can have their cervix dilate and expand at the same time. Generally, if the cervix dilation time exceeds 20 hours, it is considered abnormal.

Active phase (cervix opens from 3 cm to 10 cm)

After entering the active phase, the cervix becomes looser, softer, and more elastic, so the expansion rate is much greater than that in the critical period, and it takes about 4 hours on average. However, due to individual differences, the actual time varies, and it is normal to take from tens of minutes to several hours. Of course, generally speaking, primiparas progress better than pregnant women. At this stage, doctors can use appropriate medications for pregnant women's pain conditions.