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. 2012 Aug 16:345:e5174.
doi: 10.1136/bmj.e5174.

Risk of preterm birth after treatment for cervical intraepithelial neoplasia among women attending colposcopy in England: retrospective-prospective cohort study

Alejandra Castanon  1 , Peter Brocklehurst, Heather Evans, Donald Peebles, Naveena Singh, Patrick Walker, Julietta Patnick, Peter Sasieni; PaCT Study Group
Collaborators, Affiliations

Risk of preterm birth after treatment for cervical intraepithelial neoplasia among women attending colposcopy in England: retrospective-prospective cohort study

Alejandra Castanon et al. BMJ. .

Abstract

Objective: To explore the association between preterm delivery and treatment at colposcopy.

Design: Retrospective-prospective cohort study using record linkage.

Setting: 12 National Health Service hospitals in England.

Participants: Women who had a cervical histology sample taken between 1987 and 2009. These women were linked by hospital episode statistics to hospital obstetric records between 1998 and 2009 for the whole of England to identify singleton live births between 20-43 gestational weeks before or after cervical histology.

Main outcome measures: Proportion of preterm births (<37 weeks); the relative risk for the strength of association between preterm births and treatment for cervical intraepithelial neoplasia.

Results: 18,441 singleton births occurred: 4176 before histology and 14,265 after histology. Of the singleton births after histology, 9.0% (n=1284) were preterm compared with 6.7% of all births in England over the same period (excess risk 2.3 per 100 births, 95% confidence interval 1.8% to 2.8%). Among first births after histology, the adjusted relative risk associated with previous treatment was 1.19 (95% confidence interval 1.01 to 1.41); among first births before histology the relative risk associated with subsequent treatment was 1.47 (1.05 to 2.05). Combining these, the relative risk associated with treatment adjusted for timing relative to histology was 0.91 (0.66 to 1.26) corresponding to an absolute difference of -0.25 (-2.61 to 2.11) per 100 singleton births. Among 372 women who gave birth both before and after treatment, there were 30 preterm births after treatment and 32 before treatment (relative risk 0.94, 0.62 to 1.43).

Conclusion: 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. The increased risk may be a consequence of confounding and not caused by treatment. Although this study is reassuring for large loop excision of the transformation zone overall, it is possible that deep conisation or repeated treatment leads to an increased risk of preterm delivery.

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Conflict of interest statement

Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; and no other relationships or activities that could appear to have influenced the submitted work.

Figures

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Fig 1 Flow of women through study
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Fig 2 Proportion of preterm deliveries after colposcopy by study centre, overall, and compared with England
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Fig 3 Relative risk of preterm birth in women with a birth after compared with before colposcopy
See this image and copyright information in PMC

Comment in

References

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    1. Luesley DLS, ed. NHS cervical screening programme. Colposcopy and programme management. Guidelines for the NHS cervical screening programme. NHS Information Centre, 2004.
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    1. Albrechtsen S, Rasmussen S, Thoresen S, Irgens LM, Iversen OE. Pregnancy outcome in women before and after cervical conisation: population based cohort study. BMJ 2008;337:a1343. - PMC - PubMed
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