 The active stage of labour (or "active phase of first stage" if the previous phase is termed "latent phase of first stage") has geographically differing definitions.The World Health Organization describes the active first stage as "a period of time characterized by regular painful uterine contractions, a
substantial degree of cervical effacement and more rapid cervical dilatation from 5 cm until full dilatation for first and subsequent labours.In the US, the definition of active labour was changed from 3 to 4 cm, to 5 cm of cervical dilation for multiparous women, mothers who had given birth previously, and at 6 cm for nulliparous women, those who had not given birth before.