Objective: To examine whether surgical procedures involving the uterine cervix were associated with pregnancy outcomes, including preterm birth, low birth weight, cesarean delivery and pregnancy loss.
Design: Population-based observational study nested in retrospective matched cohort.
Setting: Kaiser Permanente Northwest integrated health plan in Oregon/Washington, U.S.A.
Population: Female health plan members age 14-53 years with documented pregnancies from 1998-2009. Women with prior excisional and ablative cervical surgical procedures (N = 322) were compared to women unexposed to cervical procedures (N = 4,307) and, separately, to those having undergone only diagnostic/biopsy procedures (N = 847).
Methods: Using log-linear regression models, we examined risk of adverse pregnancy outcomes in relation to prior excisional or ablative cervical surgical procedures. We stratified excisional procedures by excision thickness. We evaluated for confounding by age, body mass index, race, smoking history, previous preterm birth, and parity.
Results: We found a positive association between excisional treatment > = 1.0 cm and the outcomes preterm birth and low birth weight (preterm birth unadjusted risk ratio [RR] = 2.15, 95% confidence interval [CI] 1.16-3.98 for excisions ≥1.0 cm compared to unexposed women), particularly in women who delivered within one year of surgery (RR = 3.26, 95% CI 1.41-7.53). There was no clear association between excisional treatment and cesarean delivery, and treated women did not have a substantially higher risk of dysfunctional labor. Ablative treatment was not associated with low birth weight, preterm birth, or cesarean delivery but was associated with pregnancy loss (RR = 1.43, 95% CI 1.05-1.93 vs. unexposed women). Analyses using the diagnostic procedures comparison group produced similar results.
Conclusion: Women with > = 1.0 cm excisional treatment had elevated risk of preterm birth and low birth weight when compared to unexposed women and women with cervical diagnostic procedures. This suggests that increased risk derives from the treatment itself, not from other characteristics. The observed association between pregnancy loss and ablative surgical treatment requires further investigation.