© 2017 Informa UK Limited, trading as Taylor & Francis Group. Objective: To evaluate outcomes among pregnancies with cerclage as compared to cerclage and adjunctive progesterone. Methods: A retrospective cohort study was performed from 1 October 2011–30 June 2015 including women with a singleton gestation with vaginal cerclage. Exclusion criteria included multiple gestations, simultaneous 17-alpha hydroxyprogesterone caproate (17-OHPC) and vaginal progesterone (vag-p) use, and patients lost to follow-up. Primary outcome was prevention of preterm birth less than 35 (PTB <35) weeks gestational age (GA). Results: One hundred thirty-six patients met inclusion criteria; 73 women had cerclage only, 53 had cerclage and 17-OHPC, 10 had cerclage and vag-p. GA at cerclage placement was similar across groups (p = 0.068). There was a difference in prevention of PTB <35 weeks GA among groups (p = 0.035) with a trend toward earlier delivery among patients with cerclage and vag-p. Rates of PTB <35 weeks in the cerclage (29%) and cerclage and 17-OHPC groups (34%) were similar (p = 0.533). The odds ratio for risk of PTB <35 weeks among women with cerclage and vag-p as compared to all other patients was 5.21 (95%CI: 1.3–21.2). Conclusion: The combination of cerclage with intramuscular progesterone resulted in similar PTB prevention as compared to cerclage alone. There may be an association between cerclage, vaginal progesterone and higher rates of PTB which may be attributed to characteristics of the group rather than the therapies studied.