Along with other factors, midwives and doctors use the extent of cervical dilation to assist decision making during childbirth. Generally, the active first stage of labour, when the uterine contractions become strong and regular, begins when the cervical dilation is more than . The second phase of labor begins when the cervix has dilated to , which is regarded as its fullest dilation, and is when active pushing and contractions push the baby along the birth canal leading to the birth of the baby. The number of past vaginal deliveries is a strong factor in influencing how rapidly the cervix is able to dilate in labour. The time taken for the cervix to dilate and efface is one factor used in reporting systems such as the Bishop score, used to recommend whether interventions such as a forceps delivery, induction, or Caesarean section should be used in childbirth.