Intrapartum ultrasound before instrumental vaginal delivery: We still have room left to grow

Abstract

Sir, We thank Drs Dall’Asta, Rizzo and Ghi for their comments1 on our recently published randomized controlled trial evaluating the impact of intrapartum ultrasound prior to instrumental vaginal delivery on maternal and neonatal outcomes.2 Several studies have indeed reported that ultrasound provides an improved diagnosis of fetal head position in labor, compared with digital vaginal examination,3,4 but this was not a preestablished objective or outcome of our trial. Ultrasound is routinely used in our center to access occiput position when there is uncertainty following clinical examination, and this was a major detractor to recruitment of women for the trial, as several staff members felt that there was insufficient equipoise in these cases. A major question that remains unanswered, in the light of what are now several negative trials evaluating the benefit of intrapartum ultrasound for this purpose, is whether it may only be useful in cases where there is uncertainty in clinical findings. The number of cases with a head station of +3 was indeed higher in the vaginal examination group than in the ultrasound group, but the difference was not statistically significant (P = .101), suggesting it was just a chance finding. We agree that a stratification of the fetal head station at which instrumental delivery was performed would have been useful, but unfortunately the sample size did not allow it. The finding that there was a narrower angle of progression in women who required the use of two instruments or cesarean delivery is in alignment with the findings of others,5 but it remains unclear whether a favorable statistical association translates into a clinically useful and discriminatory parameter, after selection of adequate cutoff value(s). We agree with the comments related to the trial’s sample size and the limited conclusions that can be drawn from it. Given the difficulty in recruiting patients for this trial, which was also reported by others,4 we can only hope that further light will be shed on the subject from metaanalysis of the results.