The Prediction of Prolonged Pregnancy by Transvaginal Ultrasonographic Measurement

Background and Objective: Early prediction of prolonged pregnancy for prevention of fetal asphyxia is important. The present study aimed to examine transvaginal ultrasonographic measurement of the cervical length at week ۳۷ as a predictor of prolonged pregnancy. Materials and Methods: This study was a descriptive-correlated design of ultrasound examination at week ۳۷ of gestation in ۱۲۶ singleton pregnant women with cephalic presentation attending for prenatal care at the southern Tehran health antepartum clinics. The length of the cervix was measured using transvaginal ultrasound and clinical and demographic data questionnaire. Gestational age at the time of delivery was calculated. Prolonged pregnancy was defined as a pregnancy that extended beyond ۴۱ weeks of gestation. T-test, χ۲ test, Logistic Regression and receiver operating characteristic curve was used for statistical analysis using the SPSS ver. ۱۶.۰. Results: The mean cervical length was ۲۶.۱۰ ±۸.۹. The rate of pregnancy that extended beyond ۴۱ weeks of gestation in this study was ۴.۸%. The cervical length at week ۳۷ was significantly longer in women who delivered at >۴۱ weeks (n=۶) than in those delivering at ≤۴۱ weeks (n=۱۲۰), (۳۴.۰۸ mm ±۸.۵ vs. ۲۵.۷ ±۸.۷ mm P=۰.۰۲). The best cut-off value of cervical length at week ۳۷ for the prediction of prolonged pregnancy was ۲۵.۵ mm, with a sensitivity of ۱۰۰%, specificity of ۵۰%, positive predictive value of ۹%, and negative predictive value of ۱۰۰%. Conclusion: Cervical length at week ۳۷ can predict the likelihood of prolonged pregnancy, but with low positive predictive value. This information can be utilized when counseling patients regarding the management of term pregnancies.