Imaging of the pubic arch angle in prolonged second stage of labour with intrapartum translabial 3D ultrasound and its clinical significance

Aim: To evaluate the clinical significance of the pubic arch angle (PAA) measured by intrapartum translabial 3D ultrasound during prolonged second stage of labor. Also correlation to other ITU parameters and birth outcome was measured.

Materials: 42 nulliparous women at term with normally grown fetuses in cephalic presentation were evaluated. Translabial ultrasound (transverse plane) was used to measure the PAA. Correlations with fetomaternal characteristics, mode of delivery and perinatal outcome were evaluated.

Results: The mean PAA was 104.3 ° (± 12.1 °; range, 84 ° – 148 °). There was a strong correlation with the angle of progression and the head direction. There was no significant correlation with the mode of delivery. Patients with non occipitoanterior position had a significantly smaller angle (946.7 °± 3.5 ° vs. 106.2 °± 16.8 °, P < 0.05). PAA has no predictive value for the mode of delivery.

Conclusion: Three dimensional ITU is a reliable method to measure and objectify the PAA. There was strong correlation to other already well examined ITU parameters like the angle of progression and the head direction. Nonetheless, in that relatively small sample size there was no significant correlation to the mode of delivery.