Does Longer Second-Trimester Cervical Length Increase Likelihood of Labor Induction? [ID 2683543]

INTRODUCTION: Second-trimester transvaginal cervical length (TVCL) under 2.5 cm is associated with increased rates of spontaneous preterm birth; however, little is known about the effect of increasing TVCLs on spontaneous labor rates. We aimed to determine if longer TVCL is associated with increased risk of induction of labor (IOL). METHODS: This is a retrospective cohort study of patients eligible for vaginal birth with singleton term gestations and normal TVCL (at 16–24 weeks of gestation) delivering at a tertiary care center June 2022 to June 2023. Rates of IOL were compared by TVCL tertiles (T1: 2.5–3.49 cm; T2: 3.5–4.49 cm; and T3: 4.5 cm or greater). Multivariable logistic regression controlled for potential confounders. Institutional review board approval was obtained. RESULTS: Of 1,027 eligible deliveries, 594 (58%) underwent IOL. Patients with TVCLs in T2 and T3 were significantly more likely to undergo IOL than patients with TVCL in T1 (T2 59.6% versus T1 49.4%, P =.02; T3 56.5%, P =.04). Patients in T2 had increased odds of IOL compared to those in T1 (OR 1.5 [CI, 1.1–2.1]). This relationship did not remain significant after adjusting for potential confounders including term delivery, delivery mode, race/ethnicity, age, and body mass index. The odds of IOL with TVCL in T3 were not significantly different than for those in T1, before and after adjusting for confounders. CONCLUSION: Within a cohort of patients with normal mid-trimester TVCL, increasing TVCLs were not associated with higher rates of IOL after adjusting for confounding variables. These results can be used to guide patient counseling surrounding birth plans and expectations for labor and delivery.