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. 2008 Sep 18:337:a1343.
doi: 10.1136/bmj.a1343.

Pregnancy outcome in women before and after cervical conisation: population based cohort study

Susanne Albrechtsen  1 , Svein Rasmussen, Steinar Thoresen, Lorentz M Irgens, Ole Erik Iversen
Affiliations

Pregnancy outcome in women before and after cervical conisation: population based cohort study

Susanne Albrechtsen et al. BMJ. .

Abstract

Objectives: To examine the consequences of cervical conisation in terms of adverse outcome in subsequent pregnancies.

Design: Population based cohort study.

Data sources: Data on cervical conisation derived from the Cancer Registry of Norway and on pregnancy outcome from the Medical Birth Registry of Norway, 1967-2003. 15 108 births occurred in women who had previously undergone cervical conisation and 57 136 who subsequently underwent cervical conisation. In the same period there were 2 164 006 births to women who had not undergone relevant treatment (control).

Results: The proportion of preterm delivery was 17.2% in women who gave birth after cervical conisation versus 6.7% in women who gave birth before cervical conisation and 6.2% in women who had not undergone cervical conisation. The relative risk of a late abortion (<24 weeks' gestation) was 4.0 (95% confidence interval 3.3 to 4.8) in women who gave birth after cervical conisation compared with no cervical conisation. The relative risk of delivery was 4.4 (3.8 to 5.0) at 24-27 weeks, 3.4 (3.1 to 3.7) at 28-32 weeks, and 2.5 (2.4 to 2.6) at 33-36 weeks. The relative risk of preterm delivery declined during the study period and especially of delivery before 28 weeks' gestation.

Conclusion: Cervical conisation influences outcome in subsequent pregnancies in terms of an increased risk of preterm delivery, especially in the early gestational age groups in which the clinical significance is highest. A careful clinical approach should be taken in the selection of women for cervical conisation and in the clinical care of pregnancies after a cervical conisation.

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Conflict of interest statement

Competing interests: None declared.

Figures

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Fig 1 Births before and after cervical conisation or with no cervical conisation by gestational age, Norway 1967-2003
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Fig 2 Births before and after cervical conisation or with no cervical conisation by birth weight, Norway 1967-2003
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Fig 3 Relative risk of preterm birth in various gestational age groups in women who gave birth after cervical conisation compared with births to women with no cervical conisation by year of birth, Norway 1967-2003
See this image and copyright information in PMC

Comment in

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