Rapid versus stepwise application of negative pressure in vacuum extraction-assisted vaginal delivery: a multicenter randomized controlled non-inferiority trial

Objective: To evaluate whether the application of rapid negative pressure for vacuum-assisted delivery is as effective and safe as the stepwise method. Design: Randomized controlled trial. Setting: Six centers, including university, secondary and tertiary hospitals, in Thailand. Sample: In total, 662 women were randomized to rapid and stepwise groups, with 331 women in each group. Methods: Vacuum extraction was performed by applying a metal cup (Malmstrom) connected to an electric pump to the fetal head. The stepwise method consisted of four incremental steps of 0.2kg/cm2 every 2minutes to obtain a final negative pressure of 0.8kg/cm2. In the rapid method the negative pressure of 0.8kg/cm2 was applied in one step in