The uterine cervix is a remarkable structure, which plays an essential role in pregnancy. During the development of the conceptus within the uterus, the cervix usually remains firmly closed to ensure that the developing fetus attains an appropriate degree of maturity to permit extra-uterine survival. On the other hand, it prepares for labour and birth, by undergoing a process of effacement, whereby the substance of the cervix shortens and thins out. During labour, it must be stretched and dilated to a sufficient diameter, usually about 10cm at term, to allow the successful passage of the fetus through the birth canal.