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Objectives: To determine the accuracy of occiput-spine angle (OSA) measurement during the first stage of labor for predicting the course and outcome of labor.
Materials and Methods: A study was carried out in singleton pregnant women with cephalic presentation, who underwent labor between 37 weeks and 41 weeks and 6 days, from February 2018 to January 2019. Transabdominal ultrasound was performed to measure the OSA. The first examination was done at a cervical dilatation of 3-6 cm, and it was repeated at following 2 hours. The diagnostic values of the OSA as a predictor of the course and outcome of labor were analyzed.
Results: A total of 330 cases were studied, and 41 (12%) of them underwent a cesarean section due to cephalopelvic disproportion (CPD). There was no significant difference in mean OSA among the vaginal delivery and cesarean section groups (110.7 ± 11.1 degrees vs 110 ± 9.1 degrees, p = 0.649). The sensitivity of an OSA ≥ 100 degrees for predicting vaginal delivery was 83.7%, but its specificity was only 17.1%. The combination of an OSA ≥ 100 degrees, multiparity, and no induction of labor could predict vaginal delivery with a positive likelihood ratio 3.6.
Conclusion: The mean OSA among the vaginal delivery and cesarean section groups was not significantly different. The OSA alone was not a good predictor for vaginal delivery.
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