Comparison of different methods of measuring angle of progression in prediction of labor outcome

Abstract

Objectives First, to compare the manual sagittal and parasagittal and automated parasagittal methods of measuring the angle of progression (AoP) by transperineal ultrasound during labor, and, second, to develop models for the prediction of time to delivery and need for Cesarean section (CS) for failure to progress (FTP) in a population of patients undergoing induction of labor. Methods This was a prospective observational study of transperineal ultrasound in a cohort of 512 women with a singleton pregnancy undergoing induction of labor. A random selection of 50 stored images was assessed for inter‐ and intraobserver reliability of AoP measurements using the manual sagittal and parasagittal and automated parasagittal methods. In cases of vaginal delivery, univariate linear, multiple linear and quantile regression analyses were performed to predict time to delivery. Univariate and multivariate binomial logistic regression analyses were performed to predict CS for FTP in the first stage of labor. Results The intraclass correlation coefficient (ICC) for the manual parasagittal method for a single observer was 0.97 (95% CI, 0.95–0.98) and for two observers it was 0.96 (95% CI, 0.93–0.98), indicating good reliability. The ICC for the sagittal method for a single observer was 0.93 (95% CI, 0.88–0.96) and for two observers it was 0.74 (95% CI, 0.58–0.84), indicating moderate reliability for a single observer and poor reliability between two observers. Bland–Altman analysis demonstrated narrower limits of agreement for the manual parasagittal approach than for the sagittal approach for both a single and two observers. The automated parasagittal method failed to capture an image in 19% of cases. The mean difference in AoP measurements between the sagittal and manual parasagittal methods was 11°. In pregnancies resulting in vaginal delivery, 54% of the variation in time to delivery was explained in a model combining parity, epidural and syntocinon use during labor and the sonographic findings of fetal head position and AoP. In the prediction of CS for FTP in the first stage of labor, a model which combined maternal factors with the sonographic measurements of AoP and estimated fetal weight was superior to one utilizing maternal factors alone (area under the receiver‐operating‐characteristics curve, 0.80 vs 0.76). Conclusions First, the method of measuring AoP with the greatest reliability is the manual parasagittal technique and future research should focus on this technique. Second, over half of the variation in time to vaginal delivery can be explained by a model that combines maternal factors, pregnancy characteristics and ultrasound findings. Third, the ability of AoP to provide clinically useful prediction of CS for FTP in the first stage of labor is limited. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Breech progression angle: new feasible and reliable transperineal ultrasound parameter for assessment of fetal breech descent in birth canal

“…Among these, the angle of progression (AoP) is one of the most studied 18,[27][28][29][30] . Many studies have demonstrated that the AoP is a reliable and reproducible tool in the assessment of the degree of fetal head engagement in the birth canal [18][19][20][21][22][23][24][25][26][27]31,32 . To the best of our knowledge, TPU has not been used previously for the evaluation of fetuses in breech presentation.…”

Intrapartum transperineal ultrasound: angle of progression to evaluate and predict the mode of delivery and labor progression

“…However, no statistically significant difference was observed between the two methods (area under the receiver operating characteristic curve [AUC], 0.732; 95% confidence interval [CI], 0.614–0.823 vs. 0.714; 95% CI, 0.622–0.805) [ 16 ]. In a comparative research analysis of the inter- and intra-observer reliability, manual psAOP demonstrated superiority over ms-AOP and the failure rate of obtaining images using automated psAOP, measured by ultrasound devices, was highest at 19% (single observer: AUC, 0.97; 95% CI, 0.95–0.98 vs. 0.93; 95% CI, 0.88–0.96 and two observers: AUC, 0.96; 95% CI, 0.93–0.98 vs. 0.74; 95% CI, 0.58–0.84) [ 17 ].…”

“…As demonstrated by the aforementioned studies, the presence of various cutoff values for AOP indicates that the progression of labor is influenced by multiple factors. Frick et al [ 17 ] reported that in a model combining maternal height, parity, gestational age, fetal weight, and AOP, the AUC was the highest at 0.8. Thus, to determine an appropriate cutoff value for AOP, further research is warranted to investigate more comprehensive models that incorporate multiple factors and their interactions.…”

How to Reach the Best Ultrasound Performance in the Delivery Room

“…53 It is possible to get valuable information that could not be obtained in a VE, such as angle of progression (AoP) which is the angle between a line in the midline of the pubic symphysis and a line running tangentially from the anterior edge of the symphysis to the fetal skull evaluated through transperineal ultrasound (►Figure 2); the head progression distance (HPD) which is the shortest distance between the infrapubic line and the leading edge of the fetal skull, also evaluated through transperineal ultrasound; and the head direction (HD) which is the angle between the infrapubic line, perpendicular to the most caudal part of the pubic symphysis, and a line drawn perpendicular to the widest diameter of fetal head, evaluated through abdominal ultrasound. 47,54 The AoP is the most useful measure to predict the success of vaginal delivery, with the manual parasagittal technique being the most reliable, 55 in which the angle is formed between a line drawn along the superior-inferior axis of the pubic bone and a line drawn along the inferior end of the hyperechogenic pelvic bone forming the vertex of the angle with the fetal head.…”