Measurement of fetal head descent using the ‘angle of progression’ on transperineal ultrasound imaging is reliable regardless of fetal head station or ultrasound expertise

• Published in: Ultrasound in obstetrics & gynecology Vol. 35; no. 2; pp. 216 - 222
• Main Authors: Dückelmann, A. M., Bamberg, C., Michaelis, S. A. M., Lange, J., Nonnenmacher, A., Dudenhausen, J. W., Kalache, K. D.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.02.2010; Wiley
• Subjects: Adult; angle of progression; Biological and medical sciences; Clinical Competence - standards; Confidence Intervals; Delivery. Postpartum. Lactation; Feasibility Studies; Female; Fetuses; Gestational Age; Gynecology; Gynecology. Andrology. Obstetrics; Head; Head - diagnostic imaging; Head - embryology; Humans; Image Interpretation, Computer-Assisted - standards; Image processing; imaging; Investigative techniques, diagnostic techniques (general aspects); labor; Labor Presentation; Medical sciences; Midwifery - standards; Miscellaneous. Technology; Observer Variation; Obstetrics; Obstetrics - standards; Pregnancy; Reproducibility of Results; transperineal ultrasound; Ultrasonic investigative techniques; Ultrasonography, Prenatal - methods; Ultrasonography, Prenatal - standards; Ultrasound; Sonography; Head; Prognosis; Ultrasound imaging; Gynecology; Labor; Obstetrics; Pregnancy; Angle; transperineal ultrasound; Echography; Evolution; Fetus; Delivery; Reliability; angle of progression; Ultrasound
• ISSN: 0960-7692; 1469-0705; 1469-0705
• DOI: 10.1002/uog.7521

Objectives To assess whether ultrasound experience or fetal head station affects the reliability of measurement of fetal head descent using the angle of progression on intrapartum ultrasound images obtained by a single experienced operator, and to determine reliability of measurements when images were acquired by different operators with variable ultrasound experience. Methods One experienced obstetrician performed 44 transperineal ultrasound examinations of women at term and in prolonged second stage of labor with the fetus in the occipitoanterior position. Three midwives without ultrasound experience, three obstetricians with < 5 years' experience and three obstetricians with > 10 years' experience measured fetal head descent based on the angle of progression in the images obtained. The angle of progression was measured by two obstetricians in independent ultrasound examinations of 24 laboring women at term with the fetus in the cephalic position to allow assessment of the reliability of image acquisition. Intraclass correlation coefficients (ICCs) with 95% confidence interval (CI) were used to evaluate interobserver reliability and Bland–Altman analysis was used to assess interobserver agreement. Results In total, 444 measurements were performed and compared. Interobserver reliability with respect to offline image analysis was substantial (overall ICC, 0.72; 95% CI, 0.63–0.81). ICCs were 0.82 (95% CI, 0.70–0.89), 0.81 (95% CI, 0.71–0.88) and 0.61 (95% CI, 0.43–074) for observers with > 10 years', < 5 years' and no ultrasound experience, respectively. There were no significant differences between ICCs among observer groups according to ultrasound experience. Fetal head station did not affect reliability. Bland–Altman analysis indicated reasonable agreement between measurements obtained by two different operators with > 10 years' and < 5 years' ultrasound experience (bias, −1.09°; 95% limits of agreement, −8.76 to 6.58). The reliability of measurement of the angle of progression following separate image acquisition by two experienced operators was similar to the reliability of offline image analysis (ICC, 0.86; 95% CI, 0.70–0.93). Conclusions Measurement of the angle of progression on transperineal ultrasound imaging is reliable regardless of fetal head station or the clinician's level of ultrasound experience. Copyright © 2010 ISUOG. Published by John Wiley & Sons, Ltd.