active labor [L, activus, active, labor, work] , the second portion of the first stage of labor, characterized by rapid dilation and effacement, usually between 4 cm and near complete (10 cm) dilation. The progress of dilation is traditionally approximately 1 cm/hr in nulliparae and 1 to 2 cm/hr in multiparae in unfacilitated labor. See also Friedman curve, labor.
