Risk of preterm birth in women with cervical intraepithelial neoplasia grade one: a population-based cohort study.

INTRODUCTION:In this population-based register study our objective was to explore the association of cervical intraepithelial neoplasia, grade 1 and loop electrosurcigal excision procedure with preterm birth. MATERIAL AND METHODS:Our population consisted of 4759 women diagnosed with cervical intraepithelial neoplasia, grade 1 during 1997-2009 and their 3021 subsequent deliveries analyzed by loop electrosurcigal excision procedure and parity. Hospital Discharge Register was used to identify women diagnosed for cervical intraepithelial neoplasia, grade 1 and these data were linked with the Medical Birth Register data. We calculated odds ratios with 95% confidence intervals. RESULTS:Cervical intraepithelial neoplasia, grade 1 patients with loop electrosurcigal excision procedure had 54 (6.7%) subsequent preterm births and the corresponding figure among cervical intraepithelial neoplasia, grade 1 patients without loop electrosurcigal excision procedure was 116 (5.2%). This results in odds ratios 1.31 (95% confidence interval 0.94-1.83). We assessed the risk before and after diagnosis of cervical intraepithelial neoplasia, grade 1 both for patients with loop electrosurcigal excision procedure (odds ratios 1.47, 95% confidence interval 1.05-2.06) and without loop electrosurcigal excision procedure (odds ratios 0.90, 95% confidence interval 0.71-1.13). An increased risk for preterm birth after diagnosis of cervical intraepithelial neoplasia, grade 1 and loop electrosurcigal excision procedure was observed. We also compared both groups to the background population in the Medical Birth Register. For cervical intraepithelial neoplasia, grade 1 patients without loop electrosurcigal excision procedure the risk for preterm birth was not increased (odds ratios 0.95, 95% confidence interval 0.76-1.21) whereas for cervical intraepithelial neoplasia, grade 1 patients treated with loop electrosurcigal excision procedure the risk for preterm birth was increased (odds ratios 1.45, 95% confidence interval 1.02-1.92). CONCLUSIONS:Loop electrosurcigal excision procedure itself increases the risk for preterm birth. Cervical intraepithelial neoplasia, grade 1 as such does not increase the risk for preterm birth.