OP19.03: Sonographic Prediction of Length of Vacuum Deliveries: a Multicentre, Prospective Cohort Study

The aim of the study was to assess if transperineal ultrasound determining fetal station can predict duration of vacuum extractions in nulliparous women with prolonged second stage of labour. We performed a prospective cohort study in nulliparous women at term with prolonged second stage of labour in 7 European maternity units from 2013-2016. Women were included and head-perineum distance was measured with transperineal ultrasound when the birth attendant diagnosed prolonged second stage of labour after at least 45 minutes of active pushing and vacuum extraction was considered. The ultrasound operator and the birth attendants were blinded for each other's results. To evaluate differences in the time interval from start of vacuum extraction to delivery we used the Kaplan Meier method and Cox regression analyses. 222 women were included in the study. The duration of vacuum extraction was shorter in women with head-perineum distance ≤25 mm (log Rank test <0.01). The estimated median duration in women with head-perineum distance ≤25 mm was 6.0 minutes (95% C1 5.2-6.8 minutes) vs. 8.0 minutes (95% CI 7.1-8.9 minutes) in women with head-perineum distance >25 mm. Head-perineum distance was significantly associated with the duration of operative vaginal deliveries after adjusting for co-variates (BMI, Maternal age, fetal position, induction of labour, epidural, augmentation with Oxytocine). Adjusted hazard ratio was 0.96 (95% CI 0.94-0.98) for increasing head-perineum distance. Supporting information can be found in the online version of this abstract Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.