The cervix and prematurity: aetiology, prediction and prevention.

Preventing preterm delivery remains a major challenge for the 21st century. The cervix plays a fundamental role in supporting a pregnancy and preventing ascending infection from the lower genital tract. Infection is associated with early preterm delivery in about half of cases. Whatever the aetiology of preterm delivery, dilation of the cervix is a common endpoint, and transvaginal scanning of the cervix now provides a good predictor of early preterm delivery in both high- and low-risk women. Changes in the cervix are related to the detection of fetal fibronectin in the vagina, which is also an accurate predictor of delivery. However, the role of intervention in at-risk women is unclear. Elective cerclage is only effective in a minority of women, and the evidence to support its use is limited. It is currently being evaluated whether indicated cerclage, dictated by ultrasound findings, is beneficial.