Correlation of digital vaginal examination with transabdominal ultrasound to assess fetal head position during active labor

Abstract

Introduction: An accurate intrapartum assessment of the fetal head position (FHP) is considered important for the management of both normal and abnormal labors. The position of the fetal head influences the obstetric outcomes such as labor dystocia, choice of instruments for assisted delivery, and the success of vaginal delivery. It is well accepted that the FHP is an important determinant of success of vaginal delivery, with the occiput anterior (OA) positions favoring mostly good labor outcomes, while the occiput posterior (OP) and occiput transverse positions having a higher rate of instrumental delivery or cesarean section.5–7 Digital vaginal examination (DVE) for determination of FHP can be subjective and inaccurate. This study was aimed to compare transabdominal ultrasound with DVE for determination of FHP during active labor. Materials and methods: This is a prospective observational study at Vardhman Mahavir Medical College and Safdarjung Hospital. Low-risk pregnant women in active labor with singleton fetus in vertex presentation were enrolled in the study. Digital vaginal examination and transabdominal sonography were done for the assessment of FHP in the first and second stages of labor and prior to instrumental vaginal delivery. Labor and neonatal outcomes were recorded. Statistical analysis: Categorical variables were presented in number and percentage, and continuous variables were presented as mean ± standard deviation (SD) and median. Qualitative variables were correlated using Chi-square test. Interrater κ​agreement was used to find out the strength of agreement between FHP by DVE and ultrasonography (USG). A p value of <0.05 was considered statistically significant. The data were entered in MS Excel spreadsheet, and the analysis was done using Statistical Package for Social Sciences (SPSS) version 21.0. Results: The absolute agreement between DVE and transabdominal sonography for determining FHP was 55.82% in the first stage of labor, and the composite accuracy was 77.01% when FHP in DVE was assigned as correct within ±45° in transabdominal sonography (κ​ = 0.538 and p ≤ 0.0001). The absolute agreement between DVE and transabdominal sonography for determining FHP was 66.27% in the second stage of labor, and the accuracy was improved by 20.30% when FHP in DVE was assigned as correct within ±45° in transabdominal sonography (κ​ = 0.606 and p ≤ 0.0001). Ultrasound was able to correctly diagnose and facilitate instrumental delivery in the OA and occiput transverse positions. κ​ showed moderate concordance (0.560). Majority (96%) of the women chose transabdominal ultrasound as the preferred modality for the FHP assessment as it is less obtrusive procedure than DVE, while 4% women had an equivocal response. Conclusion: Digital vaginal examination can fail to detect the correct FHP due to the presence of tense bag of membranes, caput succedaneum, and molding in active labor. A higher percentage of the occiput transverse and OP positions can be misdiagnosed on vaginal examination. Transabdominal ultrasonography (TAS) should be used to correctly determine the FHP in such conditions. Clinical significance: Transabdominal ultrasonography should be used to confirm the FHP prior to instrumental delivery and cesarean section, which will facilitate correct application and prevent intrapartum complications.