The uterine cervix from adolescence to the menopause.

During adolescence the physiological transformation zone of the cervix in the virgin undergoes limited change when compared to that of girls who are sexually promiscuous; the latter often show large areas of metaplastic squamous epithelium and the development of an atypical transformation zone. During pregnancy, particularly the first, the transformation zone increases in size and acquires increased amounts of squamous metaplastic epithelium, probably due to the effect of acidic vaginal fluid on endocervical columnar epithelium. Evidence exists for the development of an atypical transformation zone during pregnancy with its own variable neoplastic potential. After delivery the atypical epithelium of the cervix may be partly or completely removed with resulting regression of the lesion. Alternatively, neoplastic potential may alter or the lesion may remain static or recur in its previous form. After the childbearing era the physiological transformation zone undergoes minimal change until the menopause when the whole cervix shrinks. As the studies described above dramatically show, the sexually promiscuous woman at all ages has an increased risk of developing cervical neoplasia; this risk seems to be the highest in the third decade of life.