P04.09: Intrapartum ultrasound and mode of delivery in prolonged second stage of labour

Abstract

To evaluate the relationship between intrapartum sonographic findings and mode of delivery in women with prolonged second stage of labour. Prospective evaluation of labouring women with prolonged second stage of labour, which was defined by pushing efforts lasting over 60 minutes regardless of epidural or parity. Eligible cases were submitted to transabdominal ultrasound (US) for the evaluation of the fetal head position and to transperineal US for the measurement of the midline angle (MLA), the head-perineum distance, the head-symphisis distance (HSD) and the angle of progression (AoP) at rest and at the acme of the pushing effort. Labour outcomes were compared in women who had spontaneous vaginal delivery (SVD) vs those who underwent obstetric intervention (OI), which included vacuum delivery and Caesarean section. Cases where OI was performed solely based on suspected fetal distress were excluded. Overall, 56 women were included. Among these, 19 (33.9%) had SVD and 37 (66.1%) underwent OI. The following differences were noted in the SVD compared with the OI group: lower median head station (1 (0 - +3) vs 1 (-2 - +3), p 0.011), higher rate of occiput anterior position (89.4% vs 57.8%, p 0.013), narrower midline angle (MLA) (24.78 ± 8.39 vs 55.32 ± 24.84, p <0.001), shorter head-symphisis distance (HSD) (15.11 ± 4.78 vs 18.99 ± 6.67, p 0.028) and wider delta-angle of progression (difference between the AoP at rest and the acme of the pushing effort) (24.28 + 11.92 vs 16.34 + 8.50, p 0.036). At multivariable regression analysis MLA was the only independent predictor of the mode of delivery (p 0.009). Below a MLA of 34.6 degrees the residual chance of OI was 41.7%. In women with prolonged second stage of labour a narrow MLA at ultrasound is the strongest predictor of SVD.