Risk of preterm birth after treatment for cervical intraepithelial neoplasia among women attending colposcopy in England: retrospective-prospective cohort study
Cite this as: BMJ 2012;345:e5174
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The paper by Castanon et al. provides data demonstrating that treatment of cervical intraepithelial neoplasia (CIN) does not significantly increase the risk of preterm birth (PTB). This study still confirms that women with CIN have an excess risk for PTB, with a relative risk of 1.31 (95% confidence interval 1.25 to 1.37) compared to the general population(1). Given the multifactorial aetiology of PTB, it is unsurprising that this increase caused by a single factor, is less then previously suggested, but still represents a major concern; an estimated 6% of those attending cervical screening had an abnormal smear in 2010-112. Therefore this increased risk is relevant to over 200,000 women in the UK each year(2), accounting for more the 4000 preterm births per year.
Furthermore, 599 deliveries at less than 20 weeks of gestation were excluded
from the analysis. An obvious hypothesis for the mechanism of preterm labour
associated with cone biposy is mechanical damage to the cervix causing cervical insufficiency. This classically presents with late second trimester loss or very early preterm birth. This paper therefore does not rule out an effect of treatment causing late miscarriages.
In spite of these findings, and as the author recognizes, excess risk of
cervical treatment may be related to the amount of tissue removed (3-5). It is
our experience, in two large UK preterm surveillance clinics, that identifying risks such as depth of biopsy or method of treatment is difficult since the information is rarely available and the notes are often difficult to trace and this is in any case an unreliable indicator of outcome. Thus the challenge of how to identify risk in treated patients when pregnant presides.
Cervical length is an excellent predictor of PTB, including in women with
prior cervical surgery and in combination with fetal fibronectin can accurately risk discriminate(6). This can reassure large numbers of women that have undergone cervical treatments (or even coloposcopy) and appropriately direct further management to those truly at risk.
The findings of this paper suggests an urgent need to evaluate the role of surveillance in these women, along with directed interventions to reduce the
risk of PTB. As treatment may not influence cervical mechanical function in
most women, commonly used interventions that reinforce the cervix, such as
cerclage or vaginal pessaries may not necessarily be the most appropriate treatment. If CIN influences endocervical integrity and therefore antimicrobial peptides and the vaginal microbiome, other interventions such as probiotics, natural antimicrobials or anti-inflammatory agents may be valuable and equally need to be investigated.
1. Castanon, A., Brocklehurst, P., Evans, H. et al. Risk of preterm birth
after treatment for cervical intraepithelial neoplasia among women attending colposcopy in England: retrospective-prospective cohort study. BMJ. 2012; 345: 5174
2. NHS Cervical Screening Programme Annual Review 2011. Fulwood House,
Old Fulwood Road, Sheffield S10 3TH. Accessed online at
www.cancerscreening.nhs.uk on 23/08/12.
3. Noehr, B., Jensen, A., Frederiksen, K. et al. Loop electrosurgical
excision of the cervix and subsequent risk for spontaneous preterm delivery:
a population-base study of singleton deliveries during a 9-month period.
AJOG. 2009; 201:33 e 1-6
4. Acharya, G., Kjeldber, I., Hansen, S.M. et al. Pregnancy outcome after
loop electrosurgical excision procedure for the management of cervical
intraepithelial neoplasia. Arch Gynaecol Obstet. 2005; 272: 109-112
5. Sadler, L., Saftlas, A., Wang, W. et al. Treatment for cervical
intraepithelial neoplasia and risk of preterm delivery. JAMA 2004;291:2100-6
6. Bolt, L.A., Chandiramani, M., De Greef, A. et al. The Value of
combined cervical length measurement and fetal fibronectin testing to
predict spontaneous preterm birth in asymptomatic high-risk women. J Matern
Fetal Neonatal Med. 2011. 24(7):928-932
Competing interests: None declared
Guys and St Thomas' NHS Hospital Trust, Division of Women's Health, Women's Health Academic Centre KHP, Westminster Bridge, London
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