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Wolfson Institute of Preventive Medicine - Barts and The London

Risk of preterm delivery after excision of the cervical transformation zone

Centre for Cancer Prevention

Principal Investigator:  Peter Sasieni,

Research Group: General


The preterm birth after cervical treatment (PaCT) study investigates whether there is an association between cervical treatment and the risk of preterm birth.

There are two phases of the study:

Phase 1 was a cohort study using data from women who had a cervical histology sample taken between 1987 and 2009 at one of twelve NHS hospitals.  These women were linked by hospital episode statistics (HES) to hospital obstetric records between 1998 and 2009 for the whole of England to identify singleton live births between 20-43 gestational weeks.  Each woman was then classified by their cervical treatment (punch biopsy or excisional treatment) and timing of treatment (before or after giving birth).

Phase 1 concluded that there was a slightly increased risk of preterm birth after excisional cervical treatment, though the risk of preterm delivery in women treated by colposcopy in England was substantially less than that in many other studies, predominantly from Nordic countries.

Phase 2 of the study is a case control study nested in Phase 1. Each woman who had a preterm birth was frequency matched to women who only had term births. Detailed pathology reports for the cervical histology samples identified in Phase 1 for those women who had a birth were collected, and used to determine the depth of excision. The relationship between depth of excision and preterm birth will be investigated.


Alex Castanon
Phone: +44 (0) 20 7882 3532