Active labor begins at 6 centimeters of cervical dilation, according to current guidelines from the American College of Obstetricians and Gynecologists (ACOG). This is the phase when your cervix opens more rapidly, contractions intensify, and your body shifts into a faster, more predictable pattern of progress toward delivery. The full journey from 0 to 10 centimeters is called the first stage of labor, and it’s split into two parts: the latent (early) phase and the active phase.
Why the Threshold Changed From 4 to 6 cm
For decades, 4 centimeters was taught as the start of active labor. That older benchmark shaped how hospitals decided when to intervene if labor seemed to stall. The problem was that many people between 4 and 6 centimeters simply weren’t progressing at the faster rate clinicians expected, and that mismatch led to interventions, including cesarean deliveries, that may not have been necessary.
ACOG’s updated clinical practice guideline, published in 2024, formally moved the threshold to 6 centimeters based on large studies showing that cervical dilation before that point is often slow, irregular, and variable from person to person. In other words, what looked like “stalled” labor at 4 or 5 centimeters was frequently just normal latent labor taking its time.
Latent Labor vs. Active Labor
The latent phase covers everything from your first real contractions up to about 6 centimeters. During this stretch, your cervix softens, thins out, and gradually opens. Progress can be unpredictable. You might dilate a centimeter in an hour, then sit at the same number for several hours. Contractions are typically milder, shorter, and spaced further apart. Many people spend this phase at home.
Once you hit 6 centimeters, the pace usually picks up. Contractions come closer together, last longer, and feel significantly stronger. The cervix tends to open at roughly 1 centimeter per hour on average, though this varies, especially for first-time mothers. Active labor continues until you reach 10 centimeters (full dilation), at which point the pushing stage begins.
How Long Active Labor Typically Lasts
The short answer: it depends on whether you’ve given birth before. First-time mothers have a median active labor of about 7.5 hours, with 90% finishing within roughly 21 hours. For those who’ve had a previous vaginal delivery, the median drops to about 3.3 hours, and 90% complete active labor within about 9 hours.
These numbers represent a wide range of normal. A first-time mother whose active labor lasts 12 or even 15 hours isn’t necessarily experiencing a complication. The older expectation that everyone should dilate on a neat, hourly schedule has been replaced by a more flexible understanding: as long as some progress is happening, labor is generally moving in the right direction.
What Active Labor Feels Like
The shift into active labor is usually unmistakable. Contractions typically come every 3 to 5 minutes, last 45 to 60 seconds, and build in intensity to the point where talking or walking through them becomes difficult. You may feel increasing pressure in your lower back and pelvis as the baby moves down. Nausea, shaking, and a sense of deep fatigue are all common and normal responses to the intensity of this phase.
The final stretch of active labor, from about 8 to 10 centimeters, is called transition. This is widely considered the most intense part of labor. Contractions during transition come every 2 to 3 minutes and last 60 to 90 seconds each, leaving very little rest in between. Rectal pressure and an urge to push often build during this window. Transition is also typically the shortest part of active labor, often lasting 30 minutes to 2 hours.
Other Measurements That Track Progress
Dilation gets the most attention, but it’s not the only thing your care team monitors. Effacement, or how thin your cervix has become, is measured as a percentage. At 0% effacement, your cervix is still thick and firm. At 100%, it’s paper-thin and fully ready for the baby to pass through. Most people are well on their way to full effacement by the time active labor begins.
Station describes how far down the baby’s head has moved into your pelvis, measured on a scale from negative numbers (high up) to positive numbers (lower and closer to delivery). Together, dilation, effacement, and station give a more complete picture of labor progress than any single number alone. Your care team checks these with a gloved hand during cervical exams, which happen periodically rather than continuously.
When Labor Stops Progressing
Sometimes dilation stalls during the active phase. Current guidelines define “arrest of labor” as no change in cervical dilation for a specific window of time once you’re at least 6 centimeters dilated and your water has broken. That window is at least 4 hours if contractions are strong and regular, or at least 6 hours if contractions need help becoming adequate. Before those time thresholds are met, a pause in progress isn’t considered a true arrest.
This definition matters because it sets a higher bar for deciding that labor has genuinely stalled rather than simply slowed down. The goal is to give the body more time before considering a cesarean delivery, particularly during a first labor when the pace can be unpredictable. Slow but ongoing progress at 5 or even 6 centimeters is not the same as labor that has stopped, and the updated criteria reflect that distinction.
Timing Your Arrival at the Hospital
Because latent labor can last many hours (or even days for some first-time mothers), most low-risk individuals are encouraged to stay home during the early phase. A commonly shared guideline is to head to the hospital or birth center when contractions are consistently about 5 minutes apart, lasting around 1 minute each, and have held that pattern for at least 1 hour. By that point, many people are approaching or have entered active labor.
Arriving too early in the latent phase can lead to a longer perceived hospital stay, more interventions to speed things along, and increased anxiety when dilation checks don’t show big jumps. That said, every pregnancy is different. If your water breaks, you notice bleeding, or something feels wrong, those are reasons to go in regardless of contraction timing or dilation.