Fig. 13. Traditional bilinear model of labor progress. The active phase of labor is described as Dilation (cm) = 10 – M^Active(time [h]). The transition point between active and latent labor, I = (10 – cervical dilation at transition [cm])/M^Active. The latent phase of labor is described as Dilation (cm) = I – M^latent((10 – I)/M^Active) .