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Cervical Conization Affects Pregnancy Outcomes

Removal of cervical tissue raised risk for future preterm delivery, severe low birth weight, and perinatal mortality.

Wide use of cervical cancer screening and subsequent treatment of cervical intraepithelial neoplasia (CIN) have significantly lowered the incidence of cervical cancer. However, removal or destruction of cervical tissue modifies the integrity of the cervix and raises the potential risk for preterm delivery. Results from two studies confirm this assumption.

In one study, researchers used data from the Norwegian birth and medical registries from 1967 to 2003 to assess the effects of cervical conization on gestational age at delivery in three cohorts: women who delivered after conization, those who delivered before conization, and those who delivered without ever undergoing conization. Among women with prior conization, 17% of deliveries were preterm (24–36 weeks’ gestation); this rate was 6.7% in women who underwent cervical conization later and was 6.2% in women who never underwent the procedure. Risk for spontaneous abortion (delivery before 32 weeks’ gestation) was three times greater in women who delivered after conization than in women who delivered without ever undergoing conization. During the period covered in the study, risk for preterm delivery (especially <28 weeks) dropped in women who underwent cervical conization, but specific changes in conization methodology during these years could not be determined.

In a second study, investigators performed a systematic review and meta-analysis of the association between cervical conization or ablation and serious adverse pregnancy outcomes (perinatal mortality, severe low birth weight [<1500 g], and preterm birth [<34 weeks’ gestation]). In general, serious adverse outcomes were rare — preterm delivery incidence was less than 1%. However, undergoing cold-knife conization nearly tripled risk for perinatal mortality and severe preterm delivery (<32 weeks) and doubled risk for severe low birth weight. Large loop excision of the transformation zone, however, was not associated significantly with higher risk for perinatal mortality, severe preterm delivery, or severe low birth weight. Laser conization and cervical diathermy were associated with excess risk for preterm delivery and low birth weight, but laser ablation was not.

Comment: These two studies substantiate the effects of cervical tissue removal on pregnancy outcomes. Women who develop CIN might have other risk factors, such as cigarette smoking, sexually transmitted infections, or bacterial vaginosis, which predispose them to adverse pregnancy outcomes. By using deliveries before conization as a comparator, Albrechtsen’s group adjusted for these potentially confounding risk factors; also, the decline in risk for preterm delivery from 1967 to 2003 might reflect a trend away from cold-knife conization. The adverse pregnancy outcomes associated with cervical excisional procedures prompted the American Society for Colposcopy and Cervical Pathology, in its 2006 Consensus Guidelines, to suggest close observation of CIN 2 as an option in very young women (21), especially those who plan to bear children. (However, recommended management of CIN 3 includes the possibility of excisional or ablative treatment [JW Womens Health Nov 29 2007].) Clinicians should discuss with patients the cancer risks associated with CIN, as well as future pregnancy risks associated with excisional treatments, and should perform the least destructive procedures whenever possible.

— Wendy S. Biggs, MD

Published in Journal Watch Women's Health October 16, 2008

Citation(s):

Albrechtsen S et al. Pregnancy outcome in women before and after cervical conisation: Population based cohort study. BMJ 2008 Sep 18; 337:a1343. (http://dx.doi.org/10.1136/bmj.a1343)

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Arbyn M et al. Perinatal mortality and other severe adverse pregnancy outcomes associated with treatment of cervical intraepithelial neoplasia: Meta-analysis. BMJ 2008 Sep 18; 337:a1284. (http://dx.doi.org/10.1136/bmj.a1284)

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