Cervical length measurement by transvaginal ultrasound at 20 to 24 weeks gestation and the timing and mode of delivery

Abstract

Objective: To study the relationship between midtrimester cervical length measurement on transvaginal ultrasonography and timing and mode of delivery. Materials and methods: A total of 200 asymptomatic antenatal women at 20 to 24 weeks gestation were recruited. Cervical assessment with transvaginal ultrasound was performed using a 5 MHz transvaginal probe. Findings of cervical assessment were then correlated with the timing and mode of delivery. Chi-square test and Odd's ratios with 95% confidence intervals were used. Results: Sixteen percent women delivered preterm. A cervical length of ≤ 30 mm had good specificity and NPV. At the cut-off value of 25 mm or less, sensitivity was 31.3%, specificity was 100%, PPV was also 100% and NPV was 88.4%. Increased cervical length on TVS (>40 mm) was associated with higher rate of cesarean section as compared to <40 mm (66% vs 34%) and this observation was statistically significant. Conclusion: Cervical length measured by TVS at midtrimester is a useful and significant predictor of the gestational age at delivery and the mode of delivery. The high negative predictive value avoids unnecessary interventions, such as tocolysis or cerclage in high-risk pregnancies.