What is effacement?
Effacement is the process by which the cervix prepares for delivery. After the baby has engaged in the pelvis, it gradually drops closer to the cervix; the cervix gradually softens, shortens and becomes thinner. You may hear phrases like "ripens," or "cervical thinning" which refer to effacement.
How is effacement measured?
Effacement is measured in percentages. For example, your health care provider may tell you that you are effaced 50%, which means you are half way to being completely effaced. When you are 100% effaced or completely effaced, your cervix is paper-thin and labor is right around the corner.
How will I know if and when I am effaced?
In your final weeks of pregnancy your health care provider will routinely check for effacement, and as soon as you arrive at your birth location, you will be checked for effacement. If you are a first time mom, your cervix will usually efface before it dilates. If you are a second time mom, your cervix will usually dilate before effacement.
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The concept of "station" denotes the degree of engagement of the fetal head as it navigates the maternal pelvis. Station is the relationship of the presenting part to an imaginary line drawn between the ischial spines of the pelvis. The ischial spines are two bony prominences that demarcate the middle of the pelvis.
Although we assess station during the last weeks of prenatal care (or in the case of preterm labor), its most frequent application is in labor. Progress in labor is assessed by means of several parameters, namely cervical consistency (soft to firm), cervical effacement (shortening), cervical position (posterior, anterior, or mid), cervical dilatation (0 to 10 cm) and station (-4 which is just coming into the pelvis to +4 station which is on the perineum or ready to be born). When the top of the fetal head (or other presenting part as in a breech presentation), arrives at the level of the ischial spines, the baby is said to be at 0 station or "engaged.”
Primigravidas (women having their first baby) typically engage before labor and may enter labor at -1, 0 or even +1 station. Multigravidas (women having their second or greater baby) often engage during labor.
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When your provider tells you about your baby’s station, she is referring to how far down his head has come into your pelvis. If your baby has dropped, but has not yet settled into your pelvis to begin his decent, it is measured in centimeters as a negative station. This negative measurement goes from -3 to -1. Once your baby has settled into your pelvis, but before he starts his descent to the birth canal, it is referred to as a zero (0) station. Once your baby starts heading towards the cervix, it is referred to as a positive station from 1 to 3. During this time it is likely that you will feel an increase of pressure and pain in your pelvic bone and vaginal area.
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