Objective: To investigate the predictive role of transvaginal ultrasonographic measurement of cervical length (CL) at 34 weeks of gestation in determining late-preterm and late-term deliveries in nulliparous women.
Methods: CL was measured by transvaginal ultrasonography at 34 weeks in 318 women (singleton, nulliparous, low-risk and vertex presentation). All women were followed-up till birth and delivered at hospital. Deliveries were classifed according to gestational week as late-preterm (34(0/7) to 36(6/7) weeks), term (37(0/7) to 40(6/7) weeks) and late-term (41(0/7) to 41(6/7) weeks).
Results: There was a significant correlation between CL at 34 weeks and gestational week at delivery (r = 0.614, p < 0.001). Receiver-operating characteristic curve analysis showed that CL measurement below 25.5 mm predicted late-preterm delivery with a sensitivity of 80.0%, specificity of 93.9%, positive predictive value (PPV) of 52.6% and negative predictive value (NPV) of 98.2%; while CL above 42.5 mm had 70.4% sensitivity, 93.5% specificity, 50.0% PPV and 97.1% NPV in prediction of late-term delivery.
Conclusion: Measurement of CL with transvaginal ultrasonography at 34 weeks of gestation can be of beneficial in predicting the risk of late-preterm and late-term deliveries in nulliparous women.
Keywords: Cervical length; transvaginal ultrasonography; week of gestation.