The cervix, which is the bottom portion of the uterus, opens when a woman has a baby, through a process called cervical dilation. The process of the cervix opening (dilating) is one way that healthcare staff track how a woman’s labor is progressing.
During labor, the cervix opens to accommodate the passage of baby’s head into the vagina, which is around 10 centimeters (cm) dilated for most term babies.
If the cervix isn’t open, for example, a woman isn’t in labor. But if her cervix is opening at a steady, regular rate, she’s in active labor and getting closer to delivering her baby.
The cervix typically dilates in a predictable way as a woman progresses through the stages of labor, as follows.
Stage 1 of labor
The first stage of labor is divided into two parts: the latent and active phases.
Latent phase of labor
The latent phase of labor is the first stage of labor. It can be thought of more as the “waiting game” stage of labor. For first-time moms, it can take a while to move through the latent phase of labor. In this stage, contractions aren’t yet strong or regular. The cervix is essentially “warming up,” softening, and shortening as it prepares for the main event.
It always helped me to picture the uterus as a balloon. Think of the cervix as the neck and opening of the balloon. As you fill that balloon up, the neck of the balloon draws up with the pressure of the air behind it, similar to the cervix.
The cervix is simply the bottom opening of the uterus drawing up and opening wider to make room for the baby.
Active stage of labor
A woman is considered to be in the active stage of labor once the cervix dilates to around 3 to 4 cm and contractions begin to get longer, stronger, and closer together.
The active stage of labor is characterized more by the rate of regular cervical dilation per hour. Your doctor will expect to see your cervix opening at a more regular rate during this stage.
How long does stage 1 of labor last?
There’s no scientific hard and fast rule for how long the latent and active phases last in women. The active stage of labor can range from a woman dilating anywhere from 0.5 cm per hour up to 0.7 cm per hour.
How fast your cervix dilates will also depend on if it’s your first baby or not. Mothers who have delivered a baby before tend to move more quickly through labor. Some women will simply progress more quickly than others. Some women may “stall” at a certain stage, and then dilate very quickly.
In general, once the active stage of labor kicks in, it’s a safe bet to expect a steady cervical dilation every hour. Many women don’t start really dilating more regularly until closer to around 6 cm. The first stage of labor ends when a woman’s cervix is fully dilated to 10 cm and fully effaced (thinned out).
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