Please cite this paper as: Stock S, Norman J. Treatments for precursors of cervical cancer and preterm labour. BJOG 2012;119:647-649. Women who have treatment for cervical cancer precursors are at an increased risk of preterm birth. It is generally thought that this risk relates to a decrease in the volume of the cervix, as in some studies the risk of preterm labour has been shown to increase with the volume of tissue removed, 1,2 and the number of procedures, 3 suggesting a 'dose response' to tissue removal. In England in 2009-2010 over 23 800 cervical excisional procedures were carried out, the majority being performed in women of childbearing age.4 Around 98% were performed by large loop excision of the transformation zone (LLETZ), which, although lower in risk than knife cone biopsy, 2 is associated with poor pregnancy outcomes, including preterm birth, spontaneous preterm labour, preterm prelabour rupture of membranes, low birthweight and perinatal mortality. 2,3,[5][6][7] Overall, LLETZ is associated with a between two-and ten-fold increased relative risk of preterm delivery, which is similar to the risk of preterm labour in a woman who has had a previous spontaneous preterm delivery.Three articles in this edition of the journal investigate the relationship between LLETZ excision and preterm delivery.8-10 Papoutsis et al. 8 used 3D transvaginal ultrasound to investigate regeneration of the cervix following LLETZ, prospectively recruiting 73 women undergoing LLETZ, and measuring cervical volume both before and 6 months after the procedure. They related cervical regeneration to the volume of tissue removed, and found that the smaller the volume of tissue excised, the greater the regeneration at 6 months. The authors used an arbitrary definition of 'incomplete regeneration', based on a deficit in cervical volume of 25% at 6 months, compared with the pretreatment volume. Removal of more than 11% of pretreatment cervical volume by LLETZ was associated with 'incomplete regeneration'. It is unclear whether this definition of incomplete regeneration has clinical significance in terms of future pregnancy outcome, but these findings support the hypothesis that increased tissue excision compromises cervical integrity.Khalid et al. 9 also provide evidence of an association between tissue excision and preterm birth. They performed a retrospective study of women with a singleton pregnancy following LLETZ, and examined the relationship between volume, length (distance from distal to proximal margin), and thickness (distance from stromal margin to surface) of the tissue removed and the gestational age at delivery. A total of 344 women were eligible for inclusion, and data was available for 321 of these. Greater specimen volume and thickness was associated with preterm birth (later than 24 weeks and less than 37 weeks of gestation). There was a three-fold increase in the risk of preterm delivery if the excision volume exceeded 6 cm 3 (RR 3.00, 95% CI 1.45-5.92), and if the thickness was >12 mm (RR 3.05, 95% CI 1.31-7.08...