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Effacement and dilatation need to occur for a baby to be born through the birth canal. Effacement means that the cervix stretches and gets thinner. Dilatation means that the cervix opens.
As labor nears,
cervix may begin to thin or stretch (efface) and open
(dilate) to prepare for the passage of the baby through the birth canal
(vagina). How fast the cervix thins and opens varies from woman to woman. In
some women, the cervix may start to efface and dilate slowly over a period of weeks. A
first-time mother often will not dilate until active labor begins.
Late in your pregnancy, your health professional may manually check
(wearing sterile gloves) how much your cervix has effaced and dilated.
During labor, contractions in your uterus open (dilate) your cervix and help move the baby into position to be born.
As the baby's head drops
down into the pelvis, it pushes against the cervix and causes the cervix to
relax and thin out, or efface.
See a picture of
Throughout your pregnancy, your cervix has
been closed and protected by a plug of mucus. When the cervix effaces, the
mucus plug is loosened and passes out of the vagina. The mucus may be tinged
with blood. This passage of the mucus plug is called "show" or "bloody show." You may or may not notice when the mucus
Effacement is described as a percentage. For
example, if your cervix is not effaced at all, it is 0% effaced. If the cervix
has completely thinned, it is 100% effaced.
After the cervix begins to efface, it
will also begin to open (cervical dilatation).
dilatation is expressed in centimeters from 0 to 10. Zero means that the cervix
is closed, and 10 means that it is completely dilated. Your cervix must be completely dilated before you can begin the pushing stage.
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November 2, 2011
Sarah Marshall, MD - Family Medicine & Kirtly Jones, MD - Obstetrics and Gynecology
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