The role of the angle of progression in the prediction of the outcome of occiput posterior position in the second stage of labor.

BACKGROUND: Occiput posterior position is the most frequent cephalic malposition, and its persistence at delivery is associated with a higher risk of maternal and perinatal morbidity. Diagnosis and management of occiput posterior position remain a clinical challenge. This is partly caused by our inability to predict fetuses who will spontaneously rotate into occiput anterior from those who will have persistent occiput posterior position. The angle of progression, measured with transperineal ultrasound, represents a reliable tool for the evaluation of fetal head station during labor. The relationship between the persistence of occiput posterior position and fetal head station in the second stage of labor has not been previously assessed. OBJECTIVE: This study aimed to evaluate the role of fetal head station, as measured by the angle of progression, in the prediction of persistent occiput posterior position and the mode of delivery in the second stage of labor. STUDY DESIGN: We recruited a nonconsecutive series of women with posterior occiput position diagnosed by transabdominal ultrasound in the second stage of labor. For each woman, a transperineal ultrasound was performed to measure the angle of progression at rest. We compared the angle of progression between women who delivered fetuses in occiput anterior position and those with persistent occiput posterior position at delivery. Receiver operating characteristics curves were performed to evaluate the accuracy of the angle of progression in the prediction of persistent occiput posterior position. Finally, we performed a multivariate logistic regression to determine independent predictors of persistent occiput posterior position. RESULTS: Overall, 63 women were included in the analysis. Among these, 39 women (62%) delivered in occiput anterior position, whereas 24 (38%) delivered in occiput posterior position (persistent occiput posterior position). The angle of progression was significantly narrower in the persistent occiput posterior position group than in women who delivered fetuses in occiput anterior position (118.3°±12.2° vs 127.5°±10.5°; P=.003). The area under the receiver operating characteristics curve was 0.731 (95% confidence interval, 0.594-0.869) with an estimated best cutoff range of 121.5° (sensitivity of 72% and specificity of 67%). On logistic regression analysis, the angle of progression was found to be independently associated with persistence of occiput posterior position (odds ratio, 0.942; 95% confidence interval, 0.889-0.998; P=.04). Finally, women who underwent cesarean delivery had significantly narrower angle of progression than women who had a vaginal delivery (113.5°±8.1 vs 128.0°±10.7; P<.001). The area under the receiver operating characteristics curve for the prediction of cesarean delivery was 0.866 (95% confidence interval, 0.761-0.972). At multivariable logistic regression analysis including the angle of progression, parity, and gestational age at delivery, the angle of progression was found to be the only independent predictor associated with cesarean delivery (odds ratio, 0.849; 95% confidence interval, 0.775-0.0930; P<.001). CONCLUSION: In fetuses with occiput posterior at the beginning of the second stage of labor, narrower values of the angle of progression are associated with higher rates of persistent occiput posterior position at delivery and a higher risk of cesarean delivery.

Reliability of transperineal ultrasound for the assessment of the angle of progression in labor using parasagittal approach versus midsagittal approach.

OBJECTIVE: To assess the inter-method agreement between midsagittal (msAoP) and parasagittal (psAoP) measurements of the angle of progression (AoP) during labor. In addition, we aimed to evaluate the correlation between AoP measurements by both midsagittal and parasagittal approaches with the mode of delivery. METHODS: We recruited a nonconsecutive series of women in active labor with a singleton uncomplicated term pregnancy with fetuses in vertex presentation. Women underwent transperineal ultrasound in the absence of uterine contractions or maternal pushing to measure both msAoP and psAoP. The inter-method agreement between the two acquisitions was then assessed. Lastly, both measurements were compared between women who had a vaginal delivery versus those who underwent cesarean section (CS). RESULTS: Overall, 151 women were included in the study. We found an excellent agreement between msAoP and psAoP (ICC 0.935; 95% CI 0.912-0.953, p < .001). On the other hand, psAoP overestimated the measurements in comparison with msAoP (101.2 ± 15.6 versus 98.2 ± 16.0, p < .001). There was a significant correlation between both methods of AoP assessment and duration of the active second stage of labor and AoP measured by either method was significantly wider in patients who delivered vaginally compared to those who had a CS. CONCLUSIONS: Our data showed a significant difference in the measured angle between the psAoP and the originally described msAoP. The automated measurements of AoP that have been introduced are designed using the parasagittal visualization of the more echogenic pubic arch, rather than the hypoechogenic pubic symphysis. We think that in the light of our data, care should be taken before applying data from midsagittal measurement in centers using the parasagittal automated approach.

Measurement of the fetal occiput-spine angle during the first stage of labor as predictor of the progress and outcome of labor.

BACKGROUND: Fetal head attitude has a substantial impact on labor progress and outcome. Fetal head deflexion is basically diagnosed by digital vaginal examination during labor. OBJECTIVES: To assess the effect of the fetal occiput-spine angle (OSA) measured through transabdominal ultrasound during the first stage of labor on the progress and outcome of labor. MATERIAL AND METHODS: A prospective cohort study conducted on 400 women with term uncomplicated singleton pregnancy with occipitoanterior position during active labor. The angle between two tangential lines to occipital bone and the vertebral body of the first cervical spine was measured during active labor. Follow up till delivery was done. The primary outcome parameter was the labor duration. Secondary outcomes included the mode of delivery, occurrence of maternal and fetal complications. RESULTS: There was a significant longer duration of both first and second stage of labor among women with OSA <126° when compared to those with OSA ≥126° (6.8 ± 2.1 and1.89 ± 0.85 versus 4.16 ± 1.63 and 0.92 ± 0.43, respectively). Women with OSA <126° had higher incidence of CS (46.3 versus 5.7%), perineal tears (10.4 versus 5.1%), vaginal tears (22.4 versus 6.3%), need for oxytocin augmentation (47.8 versus 21.3%) when compared to those with OSA ≥126. OSA at cutoff value of 126° had a sensitivity, specificity, and accuracy of 8264.6 and 78.4% and 93.79 and 92% in prediction of mode of delivery and overall complications, respectively. CONCLUSIONS: There was a significantly longer duration of both first and second stages of labor with higher rates of CS and maternal and fetal complications in women with OSA <126.