Role of Occiput Spinal Angle-A Novel Sonographic Index to predict the outcome of labour

Introduction: The attitude (relationship of head of a fetus to the cervical spine) in the first stage of labour has a significant impact on the outcome of labour. Deflexion of the fetal head is determined by digital vaginal examination during labour. However, different ultra-sonographic indexes have been developed to predict labour outcomes. Occiput spine angle (OSA) is a novel ultra-sonographic marker which can be used to predict operative delivery. Objective: To determine the effect of the occipital spinal angle measured through transabdominal ultrasound during the first stage of labour on the labour outcome. Materials and Methods: This prospective cross-sectional study was carried out at Department of Obstetrics and Gynecology Unit 2, Holy Family Hospital, Rawalpindi from June 2020 to Dec 2020 which included 380 low-risk pregnant women in the first active stage of labour. Occipital-spine angle (OSA) was defined as the angle formed by the fetal occiput and the cervical spine on the sagittal plane at the transabdominal ultrasound. For each case, the angle was calculated twice and independently by the 2 radiologists who were unaware of labour outcome to minimize intra and inter-observer error. Data were analyzed using SPSS version 23.0. P-value ≤ 0.05 was considered significant. Results: Incidence of operative delivery was 17.2%. A cut-off value of 1260125.50 of OSA had a sensitivity of 92.3% and specificity of 98.1% to predict operative delivery. Binary Logistic Regression showed that gestational age, OSA, and Head station are significant with the OR= 1.15, 0.711, and 0.32 respectively. Conclusion: OSA is a good predictor of operative delivery at a cut-off value of 1260. It should be determined at routine ultrasound booking during pregnancy. More studies should be conducted to highlight its importance.