A. In simplest terms, labor is the process of your cervix thinning out (effacement) and opening up (dilation). Thanks to those marvelous Braxton Hicks contractions, by the final weeks of pregnancy your practitioner may pronounce you to be 50 percent effaced or more. A cervix that is 100 percent effaced has gone from the shape of a thick-walled cone to that of a flat, thin cup beneath the baby's head. If you're 50 percent effaced, that means you're halfway there.
Your labor contractions will gradually open your cervix to that magical dilation measurement of 10 centimeters. When your cervix has dilated to that point (about the width of your hand), your midwife or obstetrician will tell you that it's all right to push during your contractions and deliver your baby. The fact that you're 3 centimeters dilated right now means that your cervix is already starting to open up. That's a great sign. However, when you'll actually go into the active labor phase is still a mystery. In general, though, once active labor begins, the average progress is about 1 centimeter dilation per hour for your first baby and 1 1/2 centimeters per hour for a second baby.
Originally published in You & Your Baby: Pregnancy.
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