P01.09: The occiput spine angle: a new sonographic index of fetal head deflexion during the 1st stage of labour: P01.09: The occiput spine angle: a new sonographic index of fetal head deflexion during the 1st stage of labour

It is possible to quantify the degree of fetal head deflexion during the 1st stage of labour by measuring sonographically the angle between the fetal occiput and the cervical spine (Occiput Spine Angle). The aim of this study was to assess the correlation between the width of the OSA and outcome of labour. A series of low risk pregnant women in the 1st stage of labour (4 to 6 cm) were prospectively included and submitted to suprapubic ultrasound. Among the fetuses with anterior or transverse occiput the angle formed the occipital bone and the cervical spine was measured (OSA angle). Cases with posterior occiput position were not included. Clinical management of labour was blinded to ultrasound findings the correlation between the width of the angle and the type of delivery was evaluated. Overall 108 patients with OA and OT fetal position were included in the study group. Of these 79 (73.1%) underwent spontaneous vaginal delivery whereas 29 (26.9%) were submitted to obstetric intervention (19 Caesarean sections and 10 vacuums). In this latter group compared to spontaneous vaginal delivery group the fetal OSA measured in the 1st stage of labour was significantly smaller (120.5 ± 10.3 vs. 127.4 ± 9.3; p < 0.01). The OSA seems an early sonographic predictor of labour complication as smaller values are associated to an increased risk of obstetric interventions.