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377: Predictive value of a short cervix for preterm delivery at less than 32 weeks gestation in twin pregnancy

      Objective

      To determine the utility of frequent cervical length measurement in the prediction of spontaneous preterm delivery at less than 32 weeks (PTD<32) in twin pregnancy.

      Study Design

      Retrospective review of twin pregnancies managed at a tertiary care center between 2005-2009. Cervical length was measured by transvaginal sonography every two weeks from 18-32 week. Delivery outcomes were correlated with cervical length data.

      Results

      154 twin pregnancies were studied; monoamniotic twins were excluded. 72 subjects were excluded from the analysis because they had indicated delivery <32 weeks. An average of 6 cervical length assessments were made in the remaining patients. PTD<32 occurred in 20 patients [24%]. A cervical length <2 cm at 24 weeks was associated with a likelihood ratio (LR) of PTD<32 of 10 [PPV 71%, NPV 86%]. Beyond 24 weeks, a cervical length of less than 2 cm was associated with a LR of PTD<32 of 3 [PPV 33%, NPV 90%]. There were no significant differences in these values between measurements made at 26-30 weeks.

      Conclusion

      A cervical length less than 2 cm at 24 weeks is highly predictive of PTD<32 in uncomplicated twin pregnancies. A cervical length greater than 2 cm at 24 weeks has a high negative predictive value for PTD<32 . Beyond 26 weeks, a cervical length of less than 2 cm is a common finding and the association with PTD<32 is not as robust.