VP58.01: The change of the angle of progression under maternal pushing at term and labour outcome

The aim of the study was to assess the association between fetal head descent with pushing, as measured by the changes in the angle of progression, at term and labour outcome in nulliparous women. We recruited a group of low-risk nulliparous women with singleton pregnancy at term before the onset of labour. We measured the angle of progression (AoP) at rest and at maximum Valsalva manoeuvre. The fetal head descent at pushing was calculated as the difference between AoP at Valsalva and that at rest (DAoP). Following delivery and data collection, we assessed the association between DAoP and various labour outcome, including Caesarean section (CS), various labour durations, Apgar score and admission to Neonatal Intensive Care Unit (NICU). Overall, 469 women were included in the analysis. Among these, 273 (58.2%) had spontaneous vaginal birth, 65 (13.9%) had instrumental delivery and 131 (27.9%) underwent CS. Women in the CS group were older, had narrower AoP at rest and at Valsalva, had a higher incidence of epidural administration and lower Apgar score at 1 and 5 minutes. On Pearson's correlation, AoP at rest and at Valsalva had a significant negative correlation with the duration of the first stage of labour. Lastly, the change of APD from rest to Valsalva (DAoP) showed a significant negative correlation with the active second stage of labour (Pearson's r -0.125, P value = 0.02). In nulliparous women at term before the onset of labour, narrower AoP at rest and at Valsalva, reflecting less engaged fetal head, are associated with a higher risk of Caesarean delivery. On the other hand, larger change of AoP from rest to Valsalva, reflecting more efficient maternal pushing, is associated with a shorter active second stage of labour.