Correlation between clinical fetal head station and sonographic angle of progression during the second stage of labor

Abstract Purpose: To investigate the correlation between the angle of progression and the clinical fetal head station (FHS) during the second stage of labor, and to build reference range. Materials and methods: A prospective, observational study was conducted. Women carrying singleton term pregnancies were enrolled during the second stage of labor. FHS was assessed manually by a senior obstetrician, while the angle of progression (AOP) was assessed by transperineal ultrasound (TPU). Both examiners were blinded to each other results. The correlation between the sonographic AOP and the clinical FHS was analyzed. Results: Seventy patients comprised the study group. Clinical FHS demonstrated an excellent correlation with the sonographic measurement of AOP (Pearson Correlation 0.642, p < 0.001). This correlation was best described by a cubic regression according to the formula: 123.800 + 10.290 × FHS −2.889 * FHS + 0.910, (r2 = 0.423, p < 0.001). After aggregation of the mean AOP per FHS, the relative predicte...