The cervix forms the opening of the uterus into the vagina. There is a canal through the centre of the cervix that is normally only a couple of millimetres in diameter. During pregnancy this canal is filled with a mucous plug to protect the growing foetus from anything entering the uterus through the vagina. As the cervix starts to dilate in the early stages of labour, this mucous plug becomes dislodged, and may be noticed as a slightly blood stained vaginal discharge (a show) by the mother.
(Last modified: 9th Oct 2014)