534: Exam-indicated cerclage: Does the dilation or gestational age at the time of placement affect outcome?

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For patients with painless cervical dilation in the mid-trimester, cerclage may be offered for the prevention of preterm birth. However, it is unknown if the cervical dilation or gestational age (GA) at cerclage placement are associated with outcomes. Our objective was to determine if cervical dilation and GA at the time of exam-indicated cerclage placement are associated with preterm birth. This was a retrospective cohort study of all patients who underwent exam-indicated cerclage placement at a single MFM practice between 11/2005 and 5/2017. Cervical dilation and GA at the time of cerclage placement were collected, as were demographic and obstetric outcomes. The primary outcome was delivery <36 weeks, as cerclages were typically removed between 36-37 weeks. Data were analyzed using the Student’s t-test and Chi-square test for trend. There were 39 patients identified who underwent exam-indicated cerclage. The median GA at delivery was 33 6/7 weeks (range 16 3/7 - 41 0/7), 24 (61.5%) patients delivered <36 weeks. Cervical dilation at the time of cerclage placement was significantly higher in patients who delivered <36 weeks compared to ≥36 weeks’ gestation (2.2 vs. 1.5 cm, p=0.05). Gestational age at the time of cerclage placement was similar between the two groups (20.1 vs. 20.5 weeks, p=0.55). When stratified by cervical dilation <2 cm versus ≥2 cm prior to cerclage placement, there was no significant difference in rates of preterm birth <28 and <32 weeks, though there was a significant difference between rates of preterm birth <36 weeks (Table). There was no difference in the rate of preterm birth when an exam-indicated cerclage was placed <20 vs. >20 weeks, or <22 vs. >22 weeks. Cervical dilation ≥2 cm at the time of exam-indicated cerclage is associated with an increased rate of preterm birth <36 weeks. However, even with cervical dilation of 2 cm or more, 50% delivered at 32 weeks or later. Gestational age at cerclage placement does not appear to be associated with outcomes. While limited by small numbers, this may be used to counsel patients about reasonable expectations for delivery timing when an exam-indicated cerclage is placed.