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.
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).
Stage 2 of labor
The second stage of labor begins when a woman's cervix is fully dilated to 10 centimeters. Even though a woman is fully dilated, it doesn't mean that the baby is necessarily going to be delivered immediately.
A woman may reach full cervical dilation, but the baby may still need time to move down the birth canal fully to be ready for birth. Once the baby is in prime position, it’s time to push. The second stage ends after the baby is delivered.
How long does stage 2 of labor last?
In this stage, there’s again a wide range for how long it can take for the baby to come out. It can last anywhere from minutes to hours. Women may deliver with only a few hard pushes, or push for an hour or more. Pushing occurs only with contractions, and the mother is encouraged to rest between them. At this point, the contractions will be about three minutes apart, lasting 60 to 90 seconds.
In general, pushing takes longer for first-time mothers and for mothers who have had epidurals. Epidurals can reduce the woman's urge to push and interfere with her ability to push. How long a mom is allowed to push depends on:
- the hospital's policy
- the doctor's discretion
- the health of the mom
- the health of the baby
The mother should be encouraged to change positions, squat with support, and rest between contractions. Forceps, vacuum, or cesarean delivery is considered if the baby isn’t progressing or the mother is becoming exhausted. Again, every woman and baby is different. There’s no definitive "cut-off time" for pushing.
The second stage ends with the birth of the baby.
Stage 3 of labor
The third stage of labor is perhaps the most forgotten phase. Even though the "main event" of birth has occurred with the birth of the baby, a woman's body still has important work to do. In this stage, she’s delivering the placenta.
A woman's body actually grows an entirely new and separate organ with the placenta. Once the baby is born, the placenta no longer has a function, so her body must expel it. The placenta is delivered the same way as the baby, through contractions. They may not feel as strong as the contractions that are needed to expel the baby. The doctor directs the mother to push and the delivery of the placenta is over quickly with one push.
How long does stage 3 of labor last?
The third stage of labor can last anywhere from five to 30 minutes. Putting the baby on the breast for breast-feeding will hasten this process.
After the hard work of moving through the stages of labor is finished, a woman's body will need time to return to its nonpregnant state. On average, it takes about six weeks for the uterus to return to its nonpregnant size and for the cervix to close back up.