Cervical dilation, the opening and thinning of the cervix, the lower part of the uterus, allows the baby to move into the birth canal. Alongside effacement, it indicates labor progression.
Recognizing Signs
Observable signs can suggest labor onset, though they don’t definitively confirm the extent of cervical opening.
Uterine contractions are a sign, characterized by increasing frequency, intensity, and regularity. Unlike Braxton Hicks, true labor contractions strengthen, occur closer together, and do not subside with changes in activity or position. They often feel like strong menstrual cramps or pressure in the lower back and abdomen. These contractions work to open the cervix.
“Bloody show” is a discharge of mucus mixed with blood from the vagina. This occurs as the cervix softens, thins, and opens, rupturing tiny blood vessels. The mucus plug, a protective barrier, may also be expelled. This plug can appear as a thick, jelly-like clump, sometimes clear, off-white, or tinged with color. Its loss means the cervix is changing, though labor might still be days or weeks away.
“Water breaking” signifies the rupture of the amniotic sac, releasing amniotic fluid. This can be a sudden gush or a slow trickle from the vagina. Amniotic fluid is typically clear and odorless, distinguishing it from urine. Water breaking can happen before or during contractions. If it breaks, contact a healthcare provider immediately to reduce infection risk.
Professional Assessment
While self-observed signs offer clues, a healthcare provider assesses cervical dilation and effacement through a physical examination. This is done manually, by inserting gloved fingers.
Dilation is measured in centimeters, indicating the opening’s width. A completely closed cervix is 0 cm dilated; full dilation for pushing is 10 cm. Providers approximate this by how many fingers fit into the opening. For instance, one fingertip might indicate 1 cm; two fingers with space, 4 cm.
Effacement refers to the thinning and shortening of the cervix, measured in percentages. Before effacement, the cervix is long and firm, around 3.5 to 4 centimeters. As it effaces, it shortens and thins, eventually reaching 100% effaced, or paper-thin. Dilation and effacement often occur simultaneously due to uterine contractions. A fully effaced, 10-centimeter dilated cervix marks the end of the first stage of labor.
Navigating Labor Progression
Once dilation is suspected or confirmed, knowing when to contact a healthcare provider or go to the hospital is important. For first labors, advice suggests heading to the hospital when contractions are strong, lasting 45-60 seconds, and occurring every 3-4 minutes for at least two hours. For those who have given birth before, the threshold is contractions every 5 minutes for at least one hour. If the water breaks, regardless of contractions, immediate contact with a healthcare provider or a trip to the hospital is recommended.
Labor progresses through distinct phases. Early labor, also known as the latent phase, is when the cervix dilates from 0 to about 6 centimeters. Contractions are milder and may be irregular, allowing many to remain at home. This phase can last hours or days.
Active labor begins when the cervix dilates from 6 to 10 centimeters. Contractions become more intense, frequent, and regular, lasting 45-90 seconds and occurring every 2-5 minutes. This is when medical intervention, such as pain relief, may be considered, and it is the appropriate time for a hospital or birthing center. Healthcare providers monitor progress and offer guidance.