Large loop excision of the transformation zone and preterm delivery over a decade in a major women's hospital

The success of cervical screening relies on assessment and treatment of pre-malignant disease. Large loop excision of the transformation zone (LLETZ) has been the mainstay of treatment for cervical intraepithelial neoplasia (CIN). Preterm delivery (PTD) in subsequent pregnancy is a long-term complication of the intervention.

To describe the characteristics of women who had LLETZ treatment(s) followed by PTD in the Rotunda Hospital over a 10-year period.

The pathology and the obstetric databases were searched to identify women who had LLETZ followed by PTD from 1 January 2007-31 December 2016. Details including gestation at delivery, depth of LLETZ and grade of CIN were extracted. Exclusion criteria included multiple pregnancy, and deliveries due to current pregnancy indications.

There were 97 women eligible for inclusion. Mean gestation at delivery was 33⁺² weeks. CIN 1 was diagnosed in 16, CIN 2 in 24, CIN 3 in 53, and four were negative for CIN. No microinvasive or invasive disease was identified. The average depth of excision was 9.9 mm, 11.4 mm and 8.5 mm for CIN 1, 2 and 3, respectively. The difference in depth between excisions with CIN 2 and 3 was significant (p = 0.019).

Despite having a lower mean depth of excision, women with CIN 3 comprised the majority of those who experienced PTD, suggesting that factors other than mechanical weakness are implicated in PTD for these women. This is in keeping with recent suggestions that the common denominator in high grade CIN and PTD is an altered vaginal microbiome.