Cervical dilation refers to cervical opening at the end of pregnancy in order to allow the baby to pass from the uterus. The opening of the cervix itself does not cause any symptoms but there are several signs that indicate that the opening process has started and that the labor is not far off. When the cervix begins to open, the mucus plug that seals the uterus during pregnancy will be expelled through the vagina. It may come out as a clear or cloudy, thick discharge which may sometimes be difficult to differentiate from the “ordinary“ vaginal discharge that tends to be heavier during the later stage of pregnancy. The mucus plug, however, may also come out in a single, solid piece resembling an actual plug or tinged with blood (bloody show). At the same time, you will probably also experience more frequent and intense contractions. But only a vaginal exam can determine how much your cervix has opened up and whether your baby is ready to “come out“.
During a vaginal exam, your doctor will insert the second and third finger into your vagina to examine the cervix and estimate how much it has opened up. Although the doctor will measure the cervical opening with his or her fingers, the degree of cervical dilation is usually referred in centimeters. If your cervix did not open up more than 3 centimeters (1.2 inches), your baby is not ready yet to be delivered because the cervix opens up 1 to 3 centimeters during the later stage of pregnancy, sometimes several weeks before the actual delivery. But if your cervix has dilated 4 to 7 centimeters (1.6 to 2.75 inches), you will be admitted to the hospital because it signals that the labor has started. Uterine contractions and the pressure from the baby during active labor will make the cervix dilate further reaching 10 centimeters (nearly 4 inches) just before the delivery.
In addition to measuring cervical dilation, your doctor will also measure the so-called cervical effacement or thinning of the cervix which always accompanies the opening of the cervix. The effacement is measured in percentages ranging from 0 to 100%. The higher the percentage of cervical effacement the thinner the cervix and subsequently the closer the delivery.
Unless your cervix is 10 centimeters dilated and 100% effaced, it is impossible to tell when the last stage of labor will start. There is nothing you can do to speed up the process but if quick delivery is a medical necessity, your health care team may decide to accelerate the opening of your cervix with the use of synthetic form of prostaglandin, a hormone which plays an important role in the process of cervical ripening. Since this hormone is also found in semen, sex in the last week of pregnancy is sometimes advised to speed up the process of cervical ripening naturally but there are no firm evidence that this “method“ actually works.