Transvaginal sonographic evaluation of cervical length in the second trimester as a risk factor for preterm delivery

Abstract

Background: Preterm delivery continues to be a significant obstetric problem in view of prematurity complications that an immature new born develops. Cervical length is considered to be one of the important predictors of the risk of preterm delivery. There are only a few studies evaluating cervical length as risk factor for preterm delivery in the Indian population. The present study is undertaken to estimate the risk of preterm delivery in women with cervical length < 2.5 cm measured by transvaginal sonography at 18-24 weeks of gestation in South Indian population. Methods: All booked singleton pregnancies attending the Out Patient Department OPD at SAT Hospital Trivandrum, who have the correct dating and came for anomaly scan between 18-24 weeks were included for cervical length measurement with transvaginal ultrasound scanning. Selected patients were then followed till pregnancy was terminated. The outcome of pregnancy in term of period of gestation at delivery was assessed. Results: A total of 202 antenatal patients were followed up from 18-24 weeks of gestation till their termination of pregnancy and among these 101 patients had a cervical length <2.5 cm. The mean cervical length in patients with preterm delivery (n=63) was 2.4 cm and in term delivery (n=139) was 2.91 cm respectively. Of the total patients (n=202) followed, 31.2% (n=63) had preterm delivery whereas 68.8% (n=139) had term delivery. In the 101 patients with cervical length <2.5 cm, 76.2% (n=48) had preterm delivery when compared to 23.8% (n=15) of patients with cervical length>2.5 cm (n=101). The cervical length of <2.5 cm at 18-24 weeks of gestation was found to be statistically significant (p value-<0.001) in relation to outcome of delivery. The relative risk for preterm delivery in patients with cervical length<2.5 cm was 3.2 times that of patients with >2.5cm. The history of previous preterm delivery was found to be statistically significant (p value=<0.001) for preterm labour in future pregnancies. The relative risk for preterm delivery in patients with previous history of preterm labour was 3 times when compared to patients with previous term delivery. Patients with history of UTI (urinary tract infection) had 2.3 times risk for preterm delivery and relative risk for preterm delivery in patient with vaginitis was 6.8 times. The cervical length of <2.5 cm and vaginitis are independent risk factor for preterm delivery. Conclusions: Short cervix (cervical length <2.5 cm) at 18-24 weeks of gestation is a risk factor for preterm delivery. A cervical length <2.5 cm has a relative risk of 3 for preterm delivery. Previous history of preterm birth has 3 times increased risk of preterm delivery in future pregnancies. History of urinary tract infection and vaginitis also increases risk of preterm delivery. The cervical length at 18-24 weeks, history of vaginitis and UTI were found to be independent risk factors for preterm delivery.