The journey from a cervix dilated to 5 centimeters (cm) to the full 10 cm marks the most dynamic period of the first stage of labor, often called the Active Stage. During this phase, contractions become notably stronger, longer, and more regular. Cervical dilation is the physical process of the uterus’s lower end opening to allow passage for the baby. This progression is highly variable, influenced by many factors unique to each individual labor experience.
Expected Timelines for Dilation
The speed of cervical dilation during the active phase depends largely on whether a person has given birth before. For a person giving birth for the first time (nulliparous), the expected minimum rate of progress is often cited as 1.2 centimeters per hour (cm/hr) after reaching 6 cm of dilation. A multiparous individual generally progresses faster, with an expected minimum rate of 1.5 cm/hr after 6 cm. These rates represent the lower end of what is considered normal progress, meaning many people will dilate at a faster pace.
Contemporary studies suggest that the traditional expectation of 1 cm/hr from 4 cm onward may be too fast for many healthy labors, especially before 6 cm. Progress from 4 cm to 6 cm is often much slower than the time it takes to get from 6 cm to 10 cm. The period after 6 cm is typically the most rapid and predictable part of the process. For a first-time mother, this phase can take several hours, while a person who has previously given birth may complete this stage in significantly less time.
Key Factors Influencing Dilation Speed
Several physiological and external variables can cause a person’s dilation rate to deviate from these average timelines. The position of the fetus within the pelvis is a significant factor. A baby in an optimal occipitoanterior position (facing the mother’s back) applies more direct and efficient pressure to the cervix, while a posterior position (facing forward) can lead to slower progress and more intense back pain.
The use of an epidural for pain management is another common factor that may affect the speed of labor progression. While effective for pain relief, some research suggests epidurals can slightly prolong the active phase of labor. Maternal factors, such as fatigue and hydration status, also play a role, as the uterus requires energy and adequate fluid balance to contract effectively. The strength and regularity of the uterine contractions themselves, often referred to as the “power” of labor, directly dictates the rate of cervical change.
When Dilation Stalls (Defining Protracted Labor)
Medical professionals define a lack of expected progress in the active phase as protracted labor. This diagnosis is typically made when the rate of cervical dilation falls below established minimums (e.g., less than 1.2 cm/hr for nulliparous or 1.5 cm/hr for multiparous individuals). A more concerning diagnosis is an arrest of dilation, defined as no change in cervical dilation for a specific period of time. For individuals at 6 cm or more, an arrest may be diagnosed after four hours of adequate contractions or six hours of inadequate contractions despite augmentation.
When progress halts, clinicians evaluate the three main factors affecting labor: the Power (strength of contractions), the Passenger (size and position of the baby), and the Passage (the mother’s pelvis). An inadequate contraction pattern is a common cause of slow progress and is addressed before considering issues with the baby or the pelvis. Evaluating these factors helps determine the underlying reason for the stall and guides the decision-making process for intervention.
Augmentation Methods to Encourage Progress
If protracted or arrested labor is diagnosed, interventions are often used to encourage a faster rate of dilation, a process known as augmentation. One common method is the administration of synthetic oxytocin (Pitocin) through an intravenous line. Oxytocin is a hormone given to strengthen and regulate contractions that have become weak or infrequent.
Another intervention is the Artificial Rupture of Membranes (AROM), where a provider uses a small hook to break the amniotic sac. This allows the baby’s head to press more directly on the cervix and can sometimes release natural prostaglandins, which help stimulate labor. Non-medical methods are also encouraged, such as changing maternal position frequently, including using a birthing ball or peanut ball to help open the pelvis and encourage the baby to descend. These methods aim to restore the expected progression and safely move toward full dilation.