We examined cervical dilation at time of cerclage placement and its relationship to gestational age (GA) at delivery.

We conducted a retrospective cohort study of patients undergoing physical exam or ultrasound indicated cerclage in singleton pregnancies from 2014–2024 at a tertiary care facility. Patients were stratified by cervical dilation (< 1 cm, 1–2 cm, ≥ 3 cm). The primary outcome was GA at delivery. Secondary outcomes included rates of extreme prematurity and latency to delivery. Logistic regression was performed to calculate adjusted relative risk (aRR) with 95% confidence intervals (CI).

Of 290 patients undergoing ultrasound or physical examination indicated cerclage placement, 135 (46.5%) had dilation < 1 cm, 124 (42.8%) had a dilation of 1–2 cm, and 31 (10.7%) were ≥3 cm dilated. Most patients presenting with dilation (1–2 cm and ≥3 cm) had no history of preterm birth. Dilation ≥3 cm had the lowest median GA at delivery (27.3 weeks, IQR 23.4–35.7) when compared to 1–2 cm (35.1 weeks, IQR 29.0–37.9) and < 1 cm (37.0 weeks, IQR 29.7–39.0) (p = 0.001). There were increased odds of delivery at all GA cut points for dilation ≥3 cm compared to the referent group of <1 cm dilation; the association was greatest for delivery <28 weeks (aRR 8.0, 95% CI 3.09 – 20.7). Despite this, 26% of patients in the ≥3 cm group that delivered at term.

Rates of preterm delivery are significantly increased with dilation ≥3 cm at time of cerclage placement.