Reliability and Reproducibility of Analyzing 3D Transperineal Ultrasound Volumes Obtained in the First Phase of Labor - A Pilot Study.

Purpose: The aim of this study was to investigate the reliability and reproducibility of transperineal ultrasound (TPUS) in the initial phase of labor. As TPUS is a common method, it could supplement vaginal palpation and even replace it in certain situations. In addition, we used a 4-dimensional method for the assessment of cervical effacement.

Materials and methods: 54 women in labor were included and underwent TPUS. The resulting images from the acquired 4D volumes were evaluated after the examination for the first time and a second time after 21 days. The measured values were cervical length, dilatation and effacement, the angle of progression (AoP), and head-perineum distance.

Results: 54 patients were examined. TPUS images were unable to be evaluated in 12 patients because of cervical dilatation of more than 5 cm or poor image quality. Thus, 42 measurements were included. The concordance correlation coefficients according to Lin are satisfactory overall, with one exception for cervical effacement. The accuracy component of cervical length (CCC_Lin: 0.93; accuracy: 1.00), dilatation (CCC_Lin: 0.93; accuracy: 1.00), and AoP (CCC_Lin: 0.87; accuracy: 1.00) is excellent and still high for the head-perineum distance (CCC_Lin: 0.89; accuracy: 0.96) and cervical effacement (CCC_Lin: 0.77; accuracy: 0.97).

Conclusion: TPUS is a valuable noninvasive tool with good diagnostic accuracy for the AoP, cervical length, and dilatation. Our study provides support for the use of TPUS to complement a vaginal examination. It should not replace a digital examination but should serve as a suitable alternative method for monitoring labor progression in the future.