What is the cervix? The cervix is the bottom part or neck of the uterus. The cervix opens during labor so the baby may pass through the womb into the birth canal and be born.
What is effacement? Effacement is the thinning and softening of the cervix which is measured in percentages. Usually the cervix is long, hard, and closed, and at this point the effacement would be at 0%. Towards the end of pregnancy, Braxton Hicks contractions occur (sometimes you aren’t aware that you’re having contractions) which start this effacement process. Once the cervix starts to efface, then it can start to dilate too. As effacement continues, the cervix softens, becomes mushy, and then slippery. When fully effaced at 100%, the cervix has virtually disappeared against the baby’s head.
What is dilation? Dilation is the opening up of the cervix and is measured in centimeters. A fingertip dilated means about 1 centimeter dilated. Full dilation is 10 centimeters. Once full dilation occurs, the cervix is completely gone and over the baby’s head, and the mother may push the baby out to be born.
What causes the cervix to change? The uterus is a muscle that contracts or tightens. During a contraction, the baby’s head (or other presenting part), pushes down on your cervix, causing it to dilate and efface.
Why does backward dilation sometimes happen and is it normal? First of all, yes it’s normal and is not something to be worried about. Backwards dilation can occur if the baby’s head isn’t pressing as hard on your cervix as it once was. If your labor slows down and you’re not having any contractions, the cervix can close up a little. Don’t worry, once contractions pick up, you’ll soon be dilating again. A change in dilation can occur when someone new is checking your cervix. One nurse’s five cm dilated, 85% effaced may be another nurse’s six cm dilated, 80% effaced.
You will find additional clarification of when your labor may start by reading What does being 2 centimeters dilated mean?
How long does it take the cervix to dilate 5 centimeters?
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