Active Phase Labor Active phase labor is a time of rapid change in cervical dilatation, effacement, and station. Active phase labor lasts until the cervix is completely dilated. Women in active phase labor: Are at least 4 cm dilated. Have regular, frequent contractions that are usually moderately painful. Demonstrate progressive cervical dilatation of at least 1.2-1.5 cm per hour. Usually are not comfortable with talking or laughing during their contractions.