LABOUR INDUCTION: TRANSVAGINAL SONOGRAPHIC CERVICAL LENGTH VERSUS BISHOP SCORE IN PREDICTING VAGINAL DELIVERY AT KORLE-BU TEACHING HOSPITAL

Abstract

BACKGROUND Induction of labour is a common and important obstetric intervention for averting caesarean section whiles optimizing pregnancy outcomes. Traditionally, cervical assessment for favourability of induction has been done using the Bishop Score which involves invasive digital vaginal examination; with a score greater than 6 out of 13 considered favourable. Transvaginal sonographic cervical assessment of the cervix is considered a useful stand-alone tool for cervical assessment. It is less invasive and may be comparable to the Bishop Score in predicting successful induction, given the limitations of the Bishop Score. The main objective of this study was to compare the transvaginal sonographic cervical length and the Bishop Score in the prediction of successful induction among pregnant women with low risk postdate pregnancies induced at Korle- Bu Teaching Hospital. METHODOLOGY This was an analytical cross-sectional study conducted between 1st July 2022 and 30th April 2023. The study population comprised women with low risk postdate pregnancies admitted to the maternity unit of Korle- Bu Teaching Hospital for a scheduled induction of labour. The Bishop Score and transvaginal sonographic cervical assessments were done for all participants before the start of induction. The primary outcome was the predictive abilities of the transvaginal sonographic cervical length and the Bishop Score in predicting vaginal delivery within 24 hours. Secondary outcomes included the pain scores post assessment, number of hours from induction to delivery and adverse maternal and perinatal outcomes. Data analysis was done using STATA 17. Appropriate statistical tests for comparison of categorical and continuous values were used (independent t test, Wilcoxon Rank Sum test, Chi-square test and Fisher’s exact test). Optimum cut off values were identified with Receiver Operator Characteristic Curves and the predictive values determined for both successful induction of labour and vaginal delivery. RESULT Of 184 women recruited, 168 participants were included in the final analysis. The rate of vaginal delivery was 82.1%. Successful induction occurred in 117 out of 168 participants (69.9%) with a confidence interval of 62.1-76.5. vii Bishop Score ³ 4 was predictive of both successful induction and vaginal delivery. Transvaginal sonographic cervical length £ 2.31cm was predictive of successful induction and transvaginal sonographic cervical length £ 2.5cm was predictive of vaginal delivery. The predictive values of transvaginal sonographic cervical length were (sensitivity: 48.7%, specificity: 66.7%, Area under Receiver Operator Characteristic curve: 0.5769). The predictive values of Bishop Score were (sensitivity: 80.3%, specificity: 41.2%, Area under Receiver Operator Characteristic curve: 0.6076). Ninety five percent of women preferred the transvaginal sonographic cervical length. CONCLUSION Bishop Score and transvaginal sonographic cervical length were shown to be comparable in predicting both successful induction and vaginal delivery when used for pre induction cervical assessment. Transvaginal sonographic cervical length measurement was better tolerated by patients than Bishop Score assessment. In a tertiary setting where expertise for and availability of transvaginal ultrasound exist, transvaginal sonographic cervical length may be the more desirable pre-induction cervical assessment tool or a viable alternative for patients who cannot tolerate the pain of Bishop Score assessment. vii