You perform a sterile vaginal exam and determine Susan is 5-6 cm dilated, 100% effaced, and the fetus is at zero station. You determine that Susan is now in which phase of stage one labor?

• A. Latent phase
• B. Transition phase
• C. Active phase
• D. Expulsive phase

Answer: (C)

In Stage I labor, the course is described as latent, active, and sometimes transition, and the phase is determined by how open the cervix is and how the fetus is moving through the birth canal. A cervix dilated to about 5–6 cm with complete effacement (100%) shows that labor has progressed beyond the early, slower latent phase. This fits the active phase, where dilation typically advances from roughly 4 cm up to around 7 cm and contractions are stronger and more regular. The fetus being at zero station means the presenting part has engaged in the pelvis and is at the level of the ischial spines, which commonly occurs as labor deepens into the active phase and the head begins to descend. Transition would be around 8–10 cm, with even more intense contractions and little rest, while expulsive already refers to the second stage when pushing to deliver the baby begins. So, with 5–6 cm dilation, 100% effacement, and engagement at zero station, the patient is in the active phase of Stage I labor.