Most pregnant women spend some time wondering when they will go into labor, especially as the due date draws near. When the opening of the cervix starts to widen, this is called dilation, and it is one sign that labor is approaching.
Dilation is typically measured in centimeters (cm). During active labor, the cervix fully dilates to 10 cm.
In this article, we look at what dilation is and what dilating to 1 cm signals. We also describe other signs that labor may start soon.
What is dilation and how do you know if you are dilated?
The cervix undergoes several changes during labor.
The cervix is a narrow passage that connects the uterus and the vagina. During active labor, the cervix will dilate until it reaches 10 cm.
By this time, the cervix will already have undergone several changes.
During menstruation, the cervical opening allows the lining of the uterus to exit. During pregnancy, hormones cause the mucus in the cervix to thicken, fill the opening, and form what the medical community calls a mucus plug to protect the fetus.
This plug is in place for most of the pregnancy. However, in the third trimester, the cervix will begin to soften and thin, in a process called effacement. The cervical opening also begins to widen, or dilate.
A healthcare provider usually assesses the extent of dilation and effacement during routine visits. It is not uncommon for a doctor to consider 1 cm of dilation a sign of prelabor.
When will labor start if you are 1-cm dilated?
The time between dilating to 1 cm and giving birth varies from woman to woman.
One woman may go from having a closed cervix to giving birth in a matter of hours, while another is 1–2 cm dilated for days or weeks.
Some women do not experience any dilation until they go into active labor. This means that the cervix is completely closed initially, but it widens to 10 cm as labor progresses. It is especially common in first pregnancies.
For other women, especially those who have given birth before, dilation may start a few days or weeks before labor begins.
Dilation alone is not considered a sign of labor. Rather, it is the body's way of starting to prepare for labor.
Anyone concerned about early dilation should speak with a doctor. The doctor will assess the extent of dilation and any other signs that labor is imminent.
Other signs that labor may start soon
The following are some common signs that labor has begun or will begin shortly:
More frequent contractions are a common sign that labor has begun or will begin soon.
Contractions are the tightening and releasing of the uterine muscle.
Many women experience contractions throughout a pregnancy. These are common, though they can be concerning if a person is pregnant for the first time.
When contractions happen before labor, the medical community calls them Braxton-Hicks contractions. They are the body's way of warming up the muscles responsible for delivering the baby.
The key differences between Braxton-Hicks and labor contractions involve their duration, frequency, and associated pain.
If contractions seem to occur randomly and they are painless, they are likely Braxton-Hicks contractions. Contractions that occur close to a due date are usually more frequent, longer-lasting, and painful.
The time between contractions is an important indication of labor. When contractions start to occur regularly and cause pain, let a healthcare provider know.
Losing the mucus plug
When pregnancy begins, a mucus plug seals the opening of the cervix. This plug will break apart and fall away as dilation progresses.
When the plug falls away, it may look like discharge. The color can range from clear to pink, and the plug may be slightly bloody.
A woman may go into labor within a few days or weeks of losing the mucus plug.
When labor is about to start, the membrane surrounding the baby can break and fall away. The water breaking is one of the most commonly recognized signs of labor.
It can result in a sudden gush of liquid, or only a trickle. Some women may not notice because there is so little fluid.
Notify a doctor about any fluid leakage and other symptoms, such as cramping and contractions.
To prepare for labor, the body shifts the fetus closer to the cervix.
The medical community calls this lightening, and it can occur anywhere from a few hours to a few weeks before active labor begins.
When to call a doctor
Call a doctor or midwife for advice if you think your cervix may be dilating.
A doctor or midwife usually discovers that the cervix has dilated to 1 cm during a regular exam.
Contact the doctor about any signs of labor, such as regular contractions, cramping, or the water breaking.
Depending on the extent of dilation, the doctor may recommend resting in bed or avoiding strenuous activity.
In a 2015 review, researchers studied the outcomes of 82 women admitted to the hospital for preterm labor. They found that 48 percent of the women who arrived with 0–2 cm of dilation delivered within the first 48 hours of admission. For the women to qualify, they had to be between 24 and 34 weeks pregnant.
Though the study was small, it suggests that dilating to 1 cm before the 37th week may be a risk factor for preterm labor.
Anyone experiencing signs of labor before the 37th week should speak to a healthcare provider as soon as possible.
If a person is having Braxton-Hicks contractions, the following tips can help:
- resting while lying on the back
- drinking more water
- emptying the bladder
- taking a warm shower or bath
In most cases, having 1 cm of dilation for a few weeks before delivery will cause no complications. It does not necessarily mean that a woman will go into labor immediately or even the next day.
Dilation is just one of many ways that the body prepares for labor. It alone does not mean that labor is imminent.
However, dilating to 1 cm very early in pregnancy can be a sign of preterm labor, and it is important to discuss this with a doctor.